nutrition in pregnancy - home - british nutrition foundation in pregnancy... · pregnancy are, in...

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copy 2006 British Nutrition Foundation

Nutrition Bulletin

31

28ndash59

Blackwell Publishing LtdOxford UKNBUNutrition Bulletin1471-98272005 British Nutrition Foundation

2005

31

2859

Miscellaneous

Nutrition in pregnancyC S Williamson

Correspondence

Claire Williamson Nutrition Scientist British Nutrition Foundation High Holborn House 52ndash54 High Holborn London WC1V 6RQ UK E-mail cwilliamsonnutritionorguk

BRIEFING PAPER

Nutrition in pregnancy

C S Williamson

British Nutrition Foundation London UK

SUMMARY1 INTRODUCTION2 PHYSIOLOGICAL CHANGES DURING PREGNANCY

21 Changes in body composition and weight gain22 Changes in blood composition23 Metabolic changes and adaptive responses24 Key points

3 BIRTHWEIGHT AND THE FETAL ORIGINS HYPOTHESIS

31 Factors associated with birthweight32 The fetal origins of adult disease hypothesis33 Key points

4 ESSENTIAL FATTY ACIDS AND PREGNANCY

41 Key points

5 PRE-PREGNANCY NUTRITIONAL ISSUES

51 Bodyweight and fertility52 Pre-pregnancy weight and birth outcome53 Nutritional status54 Folatefolic acid55 Key points

6 NUTRITIONAL REQUIREMENTS DURING PREGNANCY

61 Energy62 Protein63 Fat64 Carbohydrate65 Vitamins651 Vitamin A652 Thiamin riboflavin and folate653 Vitamin C654 Vitamin D66 Minerals661 Calcium662 Iron67 Key points


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7 FOOD SAFETY ISSUES DURING PREGNANCY

71 Vitamin A72 Alcohol73 Caffeine74 Foodborne illness741 Listeriosis742 Salmonella743 Toxoplasmosis744 Campylobacter75 Fish76 Food allergy77 Key points

8 DIET-RELATED CONDITIONS DURING PREGNANCY

81 Nausea and vomiting and changes in taste and appetite82 Constipation83 Anaemia84 Gestational diabetes85 Hypertensive disorders86 Key points

9 ISSUES FOR SPECIFIC GROUPS

91 Vegetarians and vegans92 Teenage pregnancy93 Dieting during pregnancy94 Key points

10 CONCLUSIONS AND RECOMMENDATIONSFURTHER INFORMATIONREFERENCES

Summary

A healthy and varied diet is important at all times in life but particularly so duringpregnancy The maternal diet must provide sufficient energy and nutrients to meetthe motherrsquos usual requirements as well as the needs of the growing fetus andenable the mother to lay down stores of nutrients required for fetal development aswell as for lactation The dietary recommendations for pregnant women are actu-ally very similar to those for other adults but with a few notable exceptions Themain recommendation is to follow a healthy balanced diet based on the

Balance ofGood Health

model In particular pregnant women should try to consume plenty ofiron- and folate-rich foods and a daily supplement of vitamin D (10

micro

gday) is rec-ommended throughout pregnancy

There are currently no official recommendations for weight gain during preg-nancy in the UK For women with a healthy pre-pregnancy weight an averageweight gain of 12 kg (range 10ndash14 kg) has been shown to be associated with thelowest risk of complications during pregnancy and labour and with a reduced riskof having a low birthweight (LBW) infant However in practice well-nourishedwomen with a normal pre-pregnancy bodyweight show wide variations in weightgain during pregnancy Low gestational weight gain increases the risk of having a

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LBW infant whereas excessive weight gain during pregnancy increases the risk ofoverweight and obesity in the mother after the birth

A birthweight of 31ndash36 kg has been shown to be associated with optimal mater-nal and fetal outcomes for a full-term infant LBW (birthweight

lt

25 kg) is asso-ciated with increased infant morbidity and mortality as well as an increased risk ofadult diseases in later life such as cardiovascular disease and type 2 diabetes Thefetal origins hypothesis states that chronic diseases in adulthood may be a conse-quence of lsquofetal programmingrsquo whereby a stimulus or insult at a critical sensitiveperiod in development has a permanent effect on structure physiology or functionHowever there is little evidence that in healthy well-nourished women the diet canbe manipulated in order to prevent LBW and the risk of chronic diseases in later life

Maternal nutritional status at the time of conception is an important determinantof fetal growth and development and therefore a healthy balanced diet is impor-tant before as well as during pregnancy It is also important to try and attain ahealthy bodyweight prior to conception [body mass index (BMI) of 20ndash25] asbeing either underweight or overweight can affect both fertility and birth outcomeIt is now well recognised that taking folic acid during the peri-conceptional periodcan reduce the incidence of neural tube defects (NTDs) and all women who maybecome pregnant are advised to take a folic acid supplement of 400

micro

gday prior toand up until the 12th week of pregnancy

The UK Committee on Medical Aspects of Food Policy (COMA) panel has estab-lished dietary reference values (DRVs) for nutrients for which there is an increasedrequirement during pregnancy This includes thiamin riboflavin folate and vita-mins A C and D as well as energy and protein The energy costs of pregnancy havebeen estimated at around 321 MJ (77 000 kcal) based on theoretical calculationsand data from longitudinal studies In practice individual women vary widely inmetabolic rate fat deposition and physical activity level so there are wide varia-tions in individual energy requirements during pregnancy In the UK the recom-mendation is that an extra 200 kcal of energy per day is required during the thirdtrimester only However this assumes a reduction in physical activity level duringpregnancy and women who are underweight or who do not reduce their activitylevel may require more

The COMA DRV panel did not establish any increment in requirements for anyminerals during pregnancy as physiological adaptations are thought to help meetthe increased demand for minerals

eg

there is an increase in absorption of calciumand iron However certain individuals will require more calcium particularly teen-agers whose skeletons are still developing Up to 50 of women of childbearing agein the UK have low iron stores and are therefore at risk of developing anaemiashould they become pregnant Moreover around 40 of women aged 19ndash34 yearscurrently have an iron intake below the lower reference nutrient intake (LRNI)Pregnant women are therefore advised to consume plenty of iron-rich foods duringpregnancy and in some cases supplementation may be necessary

There are a number of food safety issues that apply to women before and duringpregnancy It is advisable to pay particular attention to food hygiene during preg-nancy and to avoid certain foods (

eg

mould-ripened and blue-veined cheeses) inorder to reduce the risk of exposure to potentially harmful food pathogens such as


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listeria and salmonella Pregnant women and those who may become pregnant arealso advised to avoid foods that are high in retinol (

eg

liver and liver products) asexcessive intakes are toxic to the developing fetus It is also recommended that theintake of both alcohol and caffeine is limited to within current guidelines

As for the general population pregnant women should try to consume at leasttwo portions of fish per week one of which should be oil-rich However in 2004the Food Standards Agency (FSA) issued new advice on oil-rich fish consumptionand now recommends a limit of no more than two portions of oil-rich fish per weekfor pregnant women (and those who may become pregnant) Oil-rich fish is a richsource of long-chain

n-

3 fatty acids which are thought to help protect against heartdisease Furthermore these types of fatty acids are also required for fetal brain andnervous system development The upper limit on oil-rich fish consumption is toavoid the risk of exposure to dioxins and polychlorinated biphenyls (PCBs) whichare environmental pollutants Pregnant women are also advised to avoid marlinshark and swordfish and limit their intake of tuna due to the risk of exposure tomethylmercury which at high levels can be harmful to the developing nervous sys-tem of the fetus

There are certain considerations with regard to specific dietary groups duringpregnancy For example vegetarians and vegans may have difficulty meeting theirrequirements for certain vitamins and minerals particularly riboflavin vitamin B

12

calcium iron and zinc However most vegan and vegetarian women should be ableto meet their nutrient requirements during pregnancy with careful dietary planningwhile those on very restricted diets may also need to consume fortified foods orsupplements

Pregnancy during adolescence raises a number of nutritional concerns Teenagersalready have high nutrient requirements for growth and development and thereforethere is potential competition for nutrients Furthermore a large proportion ofteenage girls have low intakes of a range of nutrients that are important duringpregnancy particularly folate calcium and iron Teenagers who become pregnantoften do not take folic acid supplements either because the pregnancy is unplannedor because they are unaware of the importance of taking folic acid Teenage preg-nancy therefore presents particular challenges for health professionals

As well as following a healthy balanced diet during pregnancy staying physicallyactive is also important to promote general health and well-being and also to helpprevent excess maternal weight gain Studies that have looked at the effects of mater-nal physical activity on pregnancy outcome have been of variable quality but thereis little evidence that moderate exercise can have any adverse effects on the healthof the mother or the fetus Studies do suggest that regular aerobic exercise duringpregnancy helps improve or maintain physical fitness and body image It is recom-mended that pregnant women should continue with their usual physical activity foras long as feels comfortable and try to keep active on a daily basis

eg

by walkingSwimming is a particularly suitable form of exercise although it is advisable to avoidstrenuous or vigorous physical activity during pregnancy

Keywords

birthweight

folic acid

food safety

oil-rich

fish

pregnancy

vitamin A

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C S Williamson


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1 Introduction

Dietary recommendations for women before and duringpregnancy are in fact very similar to those for otheradults but with a few exceptions The main recommen-dation is to eat a healthy balanced diet as described inthe

Balance of Good Health

model However there aresome specific recommendations which apply to preg-nancy

eg

taking folic acid supplements to help reducethe risk of neural tube defects (NTDs) There are alsocertain recommendations with regard to food safety

eg

the avoidance of certain foods to minimise the risk offood poisoning from harmful bacteria

This briefing paper will outline the physiologicalchanges that take place during pregnancy and the influ-ence of maternal diet and nutritional status on fetal out-come The current UK dietary recommendations forwomen both prior to and during pregnancy will be dis-cussed in detail together with their evidence basis Foodsafety issues are also covered as well as diet-related con-ditions during pregnancy such as anaemia and gesta-tional diabetes Issues relating to specific groupsincluding vegetarians and teenagers are discussed in thefinal section

2 Physiological changes during pregnancy

21 Changes in body composition and weight gain

Based on data from two studies of more than 3800 Brit-ish women in the 1950s Hytten and Leitch (1971)established 125 kg as the physiological norm foraverage weight gain for a full-term pregnancy of40 weeks On average this level of weight gain wasshown to be associated with optimal reproductive out-

come and was used as the basis for estimating compo-nents of weight changes in healthy pregnant women

Table 1 shows that the fetus accounts for approxi-mately 27 of the total weight gain the amniotic fluidfor 6 and the placenta for 5 The remainder is dueto increases in maternal tissues including the uterus andmammary glands adipose tissue (fat) maternal bloodvolume and extracellular fluid but not maternal lean tis-sues Approximately 5 of the total weight gain occursin the first 10ndash13 weeks of pregnancy The remainder isgained relatively evenly throughout the rest of preg-nancy at an average rate of approximately 045 kg perweek

Hytten and Leitch (1971) estimated that for an aver-age weight gain of 125 kg approximately 335 kg of fatwould be stored by the mother (Table 1) Maternal fatdeposition is encouraged by the hormone progesteronesecretion of which rises as much as ten-fold throughoutthe course of pregnancy Fat is stored most rapidly dur-ing mid-pregnancy while the fetus is small and isthought to ensure a buffer of energy stores for late preg-nancy and during lactation The deposition of fat is notan obligatory requirement of pregnancy however indeveloped countries pregnant women usually depositfat although in highly variable amounts

More recently the World Health Organization(WHO) Collaborative Study on Maternal Anthropom-etry and Pregnancy Outcomes reviewed data on over100 000 births from 20 countries to assess anthropo-metric indicators that may be associated with poor fetaloutcomes such as low birthweight (LBW) and pre-termdelivery or poor maternal outcomes such as pre-eclampsia The WHO review showed that a birthweightof 31ndash36 kg (mean 33 kg) was associated with opti-mal fetal and maternal outcomes The range of maternal

Table 1

Components of weight gain during pregnancy

Body component Increase in weight (kg) at 40 weeks Percentage () of total weight gain

Products of Fetus 340 272conception Placenta 065 52

Amniotic fluid 080 64Maternal tissues Uterus 097 78

Mammary gland 041 33Blood 125 100Extracellular extravascular fluid 168 134

Total weight gain 1250 1000

Assumed fat deposition 335 268

Source adapted from Hytten and Leitch (1971)


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weight gains associated with this optimal birthweightwas 10ndash14 kg with an average weight gain of 12 kg(WHO 1995)

The amount of weight gain required during preg-nancy to achieve a favourable outcome is also influencedby pre-pregnancy bodyweight In 1990 the Institute ofMedicine (IOM) in the USA published a report whichre-evaluated the evidence regarding optimal weight gainduring pregnancy The report concluded that pre-preg-nancy bodyweight should be taken into account whenadvising on optimal weight gain The recommendationsfor total weight gain according to pre-pregnancy bodymass index (BMI) are shown in Table 2 For womenwith a normal pre-pregnancy BMI a weight gain ofaround 04 kg per week during the second and third tri-mesters is recommended For underweight women aweight gain of 05 kg per week is the target whereas foroverweight women 03 kg per week is recommended(IOM 1990)

There are currently no official recommendations forweight gain in the UK In practice women who are nor-mally of a healthy weight vary widely in the amount ofweight they gain during pregnancy the average is 11ndash16 kg but the variation is large (Goldberg 2002) Incases of twin or multiple pregnancies maternal weightgain tends to be greater overall and the pattern of weightgain seems to differ for example women with twinstend to gain more weight in early pregnancy (seeRosello-Soberon

et al

2005)Excessive weight gain during pregnancy is associated

with a number of complications which are similar tothose associated with overweight and obesity (

eg

ele-vated blood pressure) Moreover extreme weight gainduring pregnancy is more likely to lead to overweightand obesity in the mother post-partum Converselylow gestational weight gain in women who areunderweight or of normal weight prior to pregnancy isassociated with the risk of having a LBW baby (Gold-

berg 2002) LBW is related to an increased risk of anumber of adult diseases and this is discussed furtherin section 3

It is often assumed that breastfeeding can help womento lose excess weight that has been gained during preg-nancy However studies have shown that breastfeedingactually has a limited effect on post-partum weight andfat losses particularly in well-nourished affluentwomen and therefore not too much emphasis should beplaced on breastfeeding as a means of weight controlpost-partum (Prentice

et al

1996) A number of behav-ioural and environmental factors appear to have aneffect on post-partum weight change For example ithas been shown that women who return to work soon-est after giving birth have the greatest weight loss at6 months which may be due to either an increase inphysical activity andor restricted food access (Goldberg2002)

22 Changes in blood composition

Plasma volume begins to rise as early as the first 6ndash8 weeks of pregnancy and increases by approxi-mately 1500 ml by the 34th week The increase involume is related to fetal size but not to the size ofthe mother or to her pre-pregnant plasma volumeRed cell mass normally rises by about 200ndash250 mlduring pregnancy The increase is greater when addi-tional iron supplements are given Capacity for oxy-gen transport is raised by the increased red cell masswhich serves to meet an increased demand for oxy-gen as the fetus grows and the maternal reproductiveorgans enlarge

Plasma concentrations of lipids fat-soluble vitaminsand certain carrier proteins usually increase during preg-nancy whereas there is a fall in concentrations of albu-min most amino acids many minerals and water-soluble vitamins This fall may be partly due toincreased glomerular filtration which results inincreased urinary excretion of some amino acids severalvitamins and minerals However lower circulating con-centrations of nutrients are not generally indicative ofaltered nutritional status

23 Metabolic changes and adaptive responses

Changes in maternal hormone secretions lead tochanges in the utilisation of carbohydrate fat and pro-tein during pregnancy The fetus requires a continualsupply of glucose and amino acids for growth and ahormone produced by the placenta human chorionicsomatomammotropin is thought to encourage maternal

Table 2

The Institute of Medicine (IOM) recommended ranges for total weight gain for pregnant women

Pre-pregnancyBMI (kgm

2

)Recommendedweight gain

lt

198 125ndash18 kg198ndash26 115ndash16 kg

gt

26ndash29 7ndash115 kg

gt

29

ge

6 kg

Source IOM (1990)BMI body mass index

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tissues to make greater use of lipids for energy produc-tion increasing the availability of glucose and aminoacids for the fetus

Changes in hormone levels also help to ensure thatmaternal lean tissues are conserved and are not used toprovide energy or amino acids for the fetus The rate ofaccumulation of nitrogen rises ten-fold over the courseof pregnancy with apparently no rise in nitrogen bal-ance A 30 reduction in urea synthesis and a fall inplasma urea concentration in the last trimester of preg-nancy have been observed This suggests that maternalbreakdown of amino acids may be suppressed repre-senting a mechanism for protein sparing Evidence alsosuggests that protein may be stored in early pregnancyand used at a later stage to meet the demands of thegrowing fetus

Adaptive responses help to meet the increaseddemands for nutrients irrespective of the nutritionalstatus of the mother Such homeostatic responsesinclude increased absorption of iron and calcium Otherminerals such as copper and zinc may also showimproved absorption There is reduced urinary excre-tion of some nutrients including riboflavin and theamino acid taurine (Naismith

et al

1987)Increased secretion of the hormone aldosterone par-

ticularly towards the end of pregnancy may lead toincreased reabsorption of sodium from the renal tubuleswhich may encourage fluid retention

24 Key points

bull For women with a normal pre-pregnancy weight anaverage weight gain of 12 kg (range 10ndash14 kg) is asso-ciated with the lowest risk of complications during preg-nancy and labour and with a reduced likelihood ofhaving a LBW infantbull In practice women who are normally of a healthyweight vary widely in the amount of weight they gainduring pregnancybull There are currently no official recommendations forweight gain in the UK however in the USA there arerecommendations based on pre-pregnancy BMIbull Low gestational weight gain is associated with anincreased risk of having a LBW baby Conversely exces-sive weight gain is associated with complications duringpregnancy and an increased likelihood of overweightand obesity in the mother after the birthbull Several metabolic and hormonal changes take placeduring pregnancy that help to meet the demands of thegrowing fetus

eg

increased absorption of mineralssuch as iron and calcium

3 Birthweight and the fetal origins hypothesis

31 Factors associated with birthweight

The ideal outcome of pregnancy is the delivery of a full-term healthy infant with a birthweight of 31ndash36 kgThis birthweight range is associated with optimal mater-nal outcomes in terms of the prevention of maternalmortality and complications of pregnancy labour anddelivery and optimal fetal outcomes in terms of prevent-ing pre- and perinatal morbidity and mortality andallowing for adequate fetal growth and development(WHO 1995)

Macrosomia (birthweight

gt

45 kg) is associated withobstetric complications birth trauma and higher ratesof neonatal morbidity and mortality LBW (birthweight

lt

25 kg) is also associated with an increased risk of neo-natal morbidity and mortality LBW is a leading cause ofinfant mortality it is associated with deficits in latergrowth and cognitive development as well as pulmo-nary disease diabetes and heart disease

In the latest Health Survey for England the meanreported birthweight was 332 kg (Sproston amp Primat-esta 2003) No significant difference was found betweenthe birthweights of male (334 kg) and female (331 kg)newborns The proportion of LBW infants was 7which is in line with the 1998 figure (Macfarlane

et al

2000) This percentage has in fact remained constant inthe UK over the past two decades and is marginallyhigher than the average for Western Europe of 67(UNICEFWHO 2004)

Studies of firstborn children of mothers and daughterssuggest that genetic factors play only a small part indetermining birthweight (Carr-Hill

et al

1987) Themost important factors are the rate of fetal growth andthe duration of pregnancy Infants born prematurely(before 37 weeks of pregnancy) are generally LBWhowever a full-term infant may be born small if it wasunable to grow properly in the uterus Infants frommultiple births also tend to be smaller than singletoninfants

Lower socio-economic status is associated withadverse pregnancy outcomes including LBW and anincreased risk of neonatal and post-neonatal mortalityIn the UK there is a marked social gradient in rates ofLBW despite free antenatal care throughout the coun-try Risk factors for having a LBW baby and potentialmediating variables between low socio-economic statusand LBW are shown in Table 3 There are also ethnicdifferences in birthweight for example a higher preva-lence of LBW has been found in black women in the


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USA and Asian women living in the UK (Kramer

et al

2000) although not all ethnic groups living in devel-oped countries exhibit this pattern (Bull

et al

2003)Estimates of trends in birthweight are used to reflect

infant health and are an indicator of the future healthstatus of the adult population In the UK there hasrecently been renewed emphasis on reducing health ine-qualities through the different generations An impor-tant priority has been to reduce the gaps in infantmortality between socio-economic groups As LBW is aleading cause of infant mortality reducing the incidenceof LBW in the UK is a current focus of public healthattention (Bull

et al

2003)

32 The fetal origins of adult disease hypothesis

The theory that many diseases in adulthood may havetheir origins

in utero

has provoked much research anddebate over recent years The work of David Barker andcolleagues from the Medical Research Council (MRC)Unit in Southampton whose early work was in the fieldof cardiovascular disease (CVD) has been central to thedevelopment of the lsquofetal origins hypothesisrsquo Since thenBarker and many other research groups have investi-gated potential links between fetal growth and thedevelopment of other diseases in adult life includinghypertension type 2 diabetes obesity and cancer

The fetal origins hypothesis states that impairedintrauterine growth and development may be the rootcause of many degenerative diseases of later life It ispostulated that this occurs through the mechanism oflsquofetal programmingrsquo whereby a stimulus or insult at acritical period in early life development has a permanenteffect on the structure physiology or function of differ-ent organs and tissues (Godfrey amp Barker 2000)

There is now a substantial body of evidence linking sizeat birth with the risk of adult disease Fetal growthrestriction resulting in LBW and low weight gain ininfancy are associated with an increased risk of adultCVD hypertension type 2 diabetes and the insulin resis-tance syndrome (Fall 2005) The fetal origins hypothesisproposes that these associations reflect permanent met-abolic and structural changes resulting from undernu-trition during critical periods of early development (Fall2005) However an alternative explanation is that thereis a common underlying genetic basis to both reducedfetal growth and the risk of CVD and other diseasefactors

CVD risk is also increased if an individual experiencesan early adiposity rebound or catch-up growth duringchildhood (crossing centiles for weight and BMIupwards) There is some evidence that small size at birthis associated with abdominal obesity in adulthood andthis is exacerbated by early catch-up growth (Fall 2005)

Animal studies have shown that hypertension andinsulin resistance can be programmed

in utero

byrestricting the motherrsquos diet during pregnancy Howeverthere is currently insufficient data to determine whethermaternal nutritional status and diet influences CVD riskin humans through the mechanism of fetal program-ming The outcomes of a number of ongoing prospectivestudies in this area are anticipated in the next few years

Poor maternal diet is a major cause of LBW globallybut its impact in well-nourished populations in devel-oped countries remains unclear There is currently littleevidence that manipulating the diet of already well-nourished individuals can influence fetal growth andsubsequent birthweight and therefore it has not beenpossible to make specific dietary recommendations withthe aim of preventing LBW and adult diseases in later

Table 3

Risk factors for low birthweight (LBW) and links with low socio-economic status (SES)

Risk factor Link with low SES

Anthropometrynutritional status Short stature low pre-pregnancy BMI low gestational weight gain more common in low SES womenMicronutrient intake Low dietary intake more common in low SES womenSmoking Higher prevalence and heavier smoking among low SES womenSubstance misuse More common among low SES womenWorkphysical activity Prolonged standing and strenuous work more common among low SES womenPrenatal care Lower uptake among low SES womenBacterial vaginosis More common in low SES womenMultiple birth Less common among low SES womenPsychosocial factors More stressful life events more chronic stressors more common depression and low levels of social support in low-

SES groups

Source adapted from Bull

et al

(2003)BMI body mass index

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28ndash59

life However achieving a healthy bodyweight prior topregnancy helps to reduce the risk of having a LBWbaby These issues have been summarised in detail in arecent British Nutrition Foundation (BNF) Task Forcereport on CVD (see Fall 2005)

33 Key points

bull A birthweight of 31ndash36 kg has been shown to beassociated with optimal maternal and fetal outcomes fora full-term infantbull Macrosomia (birthweight

gt

45 kg) is associated witha number of obstetric complications as well as higherrates of neonatal morbidity and mortalitybull LBW (birthweight

lt

25 kg) is associated with anincreased risk of neonatal morbidity and mortality aswell as an increased risk of diseases in later lifebull There are a number of risk factors for having a LBWinfant including low pre-pregnancy BMI poor dietsmoking and use of alcohol or drugs during pregnancyand many of these factors are associated with low socio-economic statusbull LBW is associated with increased rates of CVDhypertension and type 2 diabetes in adulthood The fetalorigins hypothesis states that these effects may be a con-sequence of lsquofetal programmingrsquo whereby a stimulus orinsult at a critical sensitive period in development has apermanent effect on physiology structure or metabo-lism of tissues and organsbull However there is little evidence that in healthy well-nourished women the maternal diet can be manipulatedin order to prevent LBW and the risk of subsequent dis-eases in later life of the offspring

4 Essential fatty acids and pregnancy

The essential fatty acids (EFAs) linoleic (182

n-

6) andalpha-linolenic acid (183

n-

3) and their long-chainderivatives arachidonic acid (AA) and docosahexaenoic

acid (DHA) are important structural components of cellmembranes and therefore essential to the formation ofnew tissues (see Fig 1) Dietary intake is therefore vitalduring pregnancy for the development of the fetus Thelong-chain polyunsaturated fatty acids (PUFAs) are par-ticularly important for neural development and growthso an adequate supply to the fetus is essential duringpregnancy (BNF 1999) Whether there may be any ben-efit to women taking supplements containing long-chain PUFAs

eg

fish oil supplements during pregnancyis another question and has been the subject of muchdebate and recent research which is outlined in thissection

The long-chain

n-

3 fatty acid DHA can be synthe-sised from alpha-linolenic acid to a limited and probablyvariable extent but the best dietary source is oil-richfish in which it is available pre-formed In contrast it isthought that sufficient AA can be synthesised fromlinoleic acid (see Table 4 for dietary sources of EFAs)DHA is essential for the development of the brain andretina of the fetus DHA is found in very highconcentrations in the photoreceptor cells of the retina

Figure 1

The

n-

6 and

n-

3 polyunsaturated fatty acid pathways

n-6 family n-3 family

Linoleic acid Alpha-linolenic acid 182 n-6 183 n-3

183 n-6 184 n-3

203 n-6 204 n-3

Arachidonic acid (AA) Eicosapentaenoic acid (EPA) 204 n-6 205 n-3

224 n-6 225 n-3

225 n-6 Docosahexaenoic acid (DHA) 226 n-3

Table 4

Dietary sources of essential fatty acids

Rich sources Moderate sources

n-6 PUFAs Linoleic acid Vegetable oils eg sunflower corn and soybean oils and spreadsmade from these

Peanut and rapeseed oils

n-3 PUFAs Alpha-linolenic acid Rapeseed walnut soya and blended vegetable oils and walnuts Meat from grass-fed ruminants vegetables andmeateggs from animals fed on a diet enrichedin alpha-linolenic acid

EPA and DHA Oil-rich fish eg salmon trout mackerel sardines and fresh tuna Foods enriched or fortified with EPADHA

DHA docosahexaenoic acid EPA eicosapentaenoic acid PUFAs polyunsaturated fatty acids

Nutrition in pregnancy 37

copy 2006 British Nutrition Foundation Nutrition Bulletin 31 28ndash59

and is the most common fatty acid in brain cellularmembranes DHA and AA together make up more than30 of the phospholipid content of the brain and retina(BNF 1999)

The brain grows most rapidly during the third trimes-ter of pregnancy and in early infancy and consequentlythe concentration of DHA in the brain and retina of thefetus increases steadily during the last trimester An ade-quate dietary supply of long-chain PUFAs is thereforethought to be important during this time to support nor-mal growth neurological development and cognitivefunction (Uauy et al 1996)

Dietary intake of EFAs during pregnancy must be suf-ficient to meet the motherrsquos requirements as well asthose of the developing fetus There is evidence how-ever that maternal body stores of these fatty acids canbe mobilised if dietary intake is low Linoleic acid (n-6)is stored in adipose tissue in high amounts however theamount of alpha-linolenic acid (n-3) present in stores islower The fatty acid status of an infant has been foundto be highly correlated with that of its mother Duringthe course of pregnancy the concentration of EFAs inmaternal blood falls by approximately 40 Levels ofAA (n-6) fall by around 23 and of DHA (n-3) fall byan average of 52 by the time of birth At the sametime the levels of non-essential fatty acids rise and nor-malisation of these levels after delivery is slow (Al et al1995)

The DHA status of infants from multiple-births hasbeen found to be lower than that of singleton infantsand newborn infants from second and third pregnancieshave been found to have a lower DHA status than first-born infants Pre-term infants also have lower levels ofDHA compared with full-term neonates This indicatesthat under certain circumstances such as multiple preg-nancies the demands on the mother to supply long-chain PUFAs to the fetus are particularly high andtherefore supplementation may be an important consid-eration (Al et al 2000)

Evidence has been gathering that supplementationwith long-chain n-3 PUFAs eg from fish oils duringpregnancy may help to prevent premature delivery andLBW The results of several randomised clinical studieshave indicated that supplementation with fish oils con-taining DHA and eicosapentaenoic acid (EPA) may leadto modest increases in gestation length birthweight orboth (Makrides amp Gibson 2000) A review by Allen andHarris (2001) concludes that there is evidence from bothanimal and human studies that the ratio of n-3 to n-6fatty acid intake may influence gestation length and n-3fatty acid intake may be inadequate The mechanism forthis may be by influencing the balance of prostaglandins

involved in the process of parturition or by improvingplacental blood flow which may lead to improved fetalgrowth Supplementation with long-chain n-3 PUFAseg DHA may be particularly useful for preventing pre-term delivery in high-risk pregnancies (Allen amp Harris2001)

Several other recent studies have found an associationbetween long-chain n-3 PUFA intake and increased ges-tational length Olsen and Secher (2002) carried out aprospective cohort study on pregnant women in Den-mark and found that a low intake of fish was a risk fac-tor for both premature delivery and LBW A randomisedcontrolled trial carried out on a group of pregnantwomen living in Kansas City (USA) found that a higherintake of DHA (133 mgday compared with 33 mgday)in the last trimester of pregnancy was associated with asignificant increase in gestation length (Smuts et al2003)

However the most recent study carried out in thisarea has found conflicting results Oken and colleaguesexamined data from a cohort of over 2000 pregnantwomen from the Massachusetts area for associationsbetween marine long-chain n-3 PUFA and seafoodintake and length of gestation birthweight and birth-weight-for-gestational-age (as a marker for fetalgrowth) Seafood and long-chain n-3 PUFA intakes werenot found to be associated with gestation length or therisk of pre-term birth However seafood and marine n-3 PUFA intakes were found to be associated with mod-erately lower birthweight and reduced fetal growth Theauthors conclude that previous studies that have shownan association between long-chain n-3 PUFA intake andincreased birthweight have not adjusted for gestationalage so have been unable to determine whether long-chain n-3 PUFA intake influences fetal growth Theauthors acknowledge that there may be other explana-tions for example gestational length may be adverselyaffected if n-3 PUFA intake is below a certain level(Oken et al 2004) Further research is thereforerequired in order to determine how these types of fattyacids influence birth outcome

A report published by the UK Health DevelopmentAgency (HDA) has examined the evidence from reviewpapers regarding the effect of fish oil supplementationon birthweight and the risk of pre-term birth (Bull et al2003) The report concluded that the evidence withregard to the use of fish oil supplements to preventLBW was conflicting In addition the Department ofHealth (DH) advises that women should not consumefish oil supplements (eg cod liver oil) during pregnancydue to their potentially high vitamin A content (seesection 71)

38 C S Williamson


41 Key points

bull The long-chain PUFAs AA and DHA are importantfor fetal development of the brain nervous system andretina so an adequate supply is essential during preg-nancybull There is currently a lot of research interest in fish oilsupplements and their potential benefits during preg-nancy There is some evidence that increasing the intakeof long-chain n-3 PUFAs during pregnancy (eg fromfish oils) may have beneficial effects on birthweight andthe duration of pregnancy however not all studies haveproduced consistent resultsbull The best dietary source of long-chain n-3 PUFAs isoil-rich fish and regular consumption of oil-rich fish isrecommended during pregnancy (up to two portions perweek) However taking cod liver oil supplements is notadvised during pregnancy as they can contain high levelsof vitamin A (see section 71)

5 Pre-pregnancy nutritional issues

51 Bodyweight and fertility

It has now been established that fertility in women isaffected by their percentage body fat rather thanabsolute bodyweight The average body fat content inwomen is 28 of bodyweight and research has shownthat a body fat content of at least 22 is necessary fornormal ovulatory function and menstruation (Thomas2001) Women who maintain a low bodyweight whohave suffered from eating disorders or who diet regu-larly often have irregular menstrual cycles and thereforemay take longer to conceive (Goldberg 2002) Gainingweight restores fertility indicating that the relativelyhigh percentage of body fat in females compared withmales may influence reproduction directly

However excessive stores of body fat can also impairfertility A prospective study of healthy women present-ing for treatment using artificial insemination found alower rate of pregnancy among obese women(BMI gt 30) than lean women (BMI lt 20) Women witha BMI of 20ndash25 had the highest rate of pregnancy(Zaadstra et al 1993) The study also showed that bodyfat distribution may be related to fertility Women withabdominal fat distribution (waist to hip ratio 08 andabove) were less likely to conceive than women withperipheral fat distribution (waist to hip ratio less than08) The deposition of excess fat in central depots hadmore impact on reduced fertility than age or severity ofobesity This could be due to insulin resistance which isassociated with abdominal fat distribution and its effect

on androgenic hormones and luteinising hormonewhich might reduce the viability of the egg

In a prospective study carried out by Clark et al(1998) a group of overweight anovulatory women inAustralia undertook a weekly programme aimed at lif-estyle changes in relation to diet and physical activitylasting 6 months Those who completed the programmelost an average of 102 kg This was shown to lead torestored ovulation conception and a successful preg-nancy in the majority of cases

52 Pre-pregnancy weight and birth outcome

It is recommended that women who are planning a preg-nancy should attempt to reach a healthy bodyweight(BMI of 20ndash25) before they become pregnant as beingoverweight or obese or underweight prior to concep-tion is associated with an increased risk of a number ofcomplications (see Goldberg 2002)

Mothers with a low BMI prior to and during pregnancyare at an increased risk of having a LBW infant (see alsosection 21) Being underweight is also associated with anincreased risk of morbidity and mortality in the newborninfant (IOM 1990) and an increased risk of degenerativediseases in later life of the offspring (see section 3)

Being overweight or obese prior to and during preg-nancy is associated with an increased risk of severalcomplications including gestational diabetes preg-nancy-induced hypertension pre-eclampsia and congen-ital defects Obesity is also linked to a greater risk ofabnormal labour and an increased likelihood of needingan emergency caesarean operation Infants born pre-term to a mother who is obese are also less likely to sur-vive (Goldberg 2002) Moreover the incidence of thesecomplications appears to increase as the pre-pregnancyBMI increases so women who are severely obese are atthe greatest risk of experiencing such complications(Galtier-Dereure et al 1995)

As the prevalence of overweight and obesity in the UKis on the increase such complications are a major causeof concern Currently 44 of women aged 25ndash34 in theUK are classified as overweight or obese (BMI gt 25)(Henderson et al 2003a) Dieting to lose weight is notadvisable during pregnancy therefore it is importantthat women who are overweight or obese shouldattempt to reach a healthy bodyweight (ie a BMI of20ndash25) before trying to conceive

53 Nutritional status

It is now well established that maternal nutritional sta-tus at the time of conception is an important determi-



nant of embryonic and fetal growth The embryo is mostvulnerable to the effects of poor maternal diet during thefirst few weeks of development often before pregnancyhas been confirmed Cell differentiation is most rapid atthis time and any abnormalities in cell division cannotbe corrected at a later stage Most organs although verysmall have already been formed 3ndash7 weeks after the lastmenstrual period and any teratogenic effects (includingabnormal development) may have occurred by this time

Improving nutritional status in women prior to preg-nancy has a beneficial influence on subsequent birth out-comes (Caan et al 1987) If all women of childbearingage were to eat a varied and adequate diet this wouldhelp to correct any nutritional imbalances and wouldhelp to ensure that the fetus has the best nutritionalenvironment in which to develop Attention to the dietat this stage also sets appropriate dietary habits to befollowed throughout pregnancy

The Food Standards Agency (FSA) provides dietaryadvice for women planning a pregnancy (see FSA2005a) The general dietary recommendations are sim-ilar to the advice given to non-pregnant women in termsof following a healthy varied and balanced diet toensure an adequate intake of energy and nutrientsThere is also an additional emphasis on consumingplenty of iron- and folate-rich foods Women who maybecome pregnant are also advised to take a folic acidsupplement of 400 microg per day (see section 54)

It is also recommended that women who are planningto have a baby should try to limit their alcohol and caf-feine intakes and avoid taking vitamin A supplementsor foods containing high levels of vitamin A (such asliver and liver products) Fish including oil-rich fishshould be included in the diet however certain types offish (shark swordfish and marlin) should be avoidedand tuna intake should be limited because of possiblecontamination See section 7 for background and fur-ther information on food safety issues both prior to andduring pregnancy

54 Folatefolic acid

It is now well recognised that folic acid (the syntheticform of the vitamin folate) is of critical importance bothpre- and peri-conceptionally in protecting against neuraltube defects (NTDs) in the developing fetus The neuraltube develops into the spine and NTDs occur when thebrain and skull andor the spinal cord and its protectivespinal column do not develop properly within the first4 weeks after conception The most common NTDs areanencephaly which results in stillbirth or death soonafter delivery and spina bifida which may lead to a

wide range of physical disabilities including partial ortotal paralysis

There are variations in the prevalence of NTDswhich depend on demographic ethnic and social fac-tors and environmental factors also seem to influencethe risk In 1998 93 children were recorded as beingborn with NTDs in the UK The incidence of affectedpregnancies is difficult to determine However it wasestimated that in 2002 there were at least 551ndash631NTD-affected pregnancies in the UK and the incidencechanged little over the 1990s (SACN 2005)

Differences in mean serum folate levels betweenNTD-affected pregnancies and unaffected pregnancieswere first reported by the Leeds Pregnancy NutritionStudy in 1976 leading researchers to conclude thatfolate deficiency may be significant in the causation ofNTDs (Smithells et al 1976) Subsequent interventionstudies in women who had previously given birth to aninfant with a NTD found that folic acid supplementa-tion in the peri-conceptional period significantlyreduced the incidence of further NTD-affected pregnan-cies (eg Smithells et al 1980)

There is now conclusive evidence from a number ofrandomised controlled trials that folic acid supplemen-tation can prevent NTDs (DH 2000) The definitivestudy was a randomised double-blind prevention trialcarried out by the MRC in multiple centres across sevencountries which established that folic acid supplemen-tation (4 mgday) before conception had a 72 protec-tive effect on the incidence of NTDs in pregnancy (MRCVitamin Study Research Group 1991)

Furthermore a recent study by Wald (2004) indicatesthat there is an inverse dosendashresponse relationshipbetween folate status and the risk of NTDs Thisresearch emphasises the critical importance of folic acidsupplementation before the time of conception as oncepregnancy is established it is probably too late for folicacid to have a protective effect (Buttriss 2004) Wald hasestimated that supplementation with 400 microg (04 mg) offolic acid per day results in a reduction in the incidenceof NTDs of 36 Supplementation with 4 mg per day isestimated to prevent 80 of NTDs (Wald 2004)

The mechanism by which folate supplementation mayhelp to prevent NTDs has not been clearly establishedA recent study carried out in the USA has shown thatwomen with a current or previous pregnancy affected byNTDs are more likely to have serum-containing autoan-tibodies against folate receptors These autoantibodiescan bind to folate receptors and block the cellularuptake of folate Further research is required to deter-mine whether this observed association is causal to thedevelopment of NTDs (Rothenberg et al 2004)

40 C S Williamson


The Department of Health (DH) currently recom-mends that all women of childbearing age who maybecome pregnant should take a supplement of 400 microg offolic acid per day until the 12th week of pregnancy andtry to consume foods which are naturally rich in folate(eg green vegetables oranges) as well as foods fortifiedwith folic acid such as some breads and breakfast cere-als Women who realise they are pregnant and have notbeen taking folic acid should start taking it immediatelyand continue until the 12th week of pregnancy Addi-tionally women who have a family history of NTDs andwho may become pregnant may be advised by theirdoctor to take a larger supplement of 5 mg (5000 microg)per day again until the 12th week of pregnancy (DH1992 2000)

This emphasis on supplementation is due to the factthat the extra folate required peri-conceptionally is dif-ficult for women to obtain through the diet alone Folicacid (the synthetic form) is also more bioavailable thanthe natural folates found in food hence foods fortifiedwith folic acid are also an important source of the vita-min Table 5 gives some examples of the folate contentof a range of foods Important sources include yeastextract green leafy vegetables oranges pulses and for-tified bread and breakfast cereals Liver is a rich sourcebut consumption of liver and liver products is not rec-ommended during pregnancy (see section 71)

Although there have been several government cam-paigns to increase awareness of the importance of folicacid supplementation many pregnancies are stillunplanned and in these cases women often do not starttaking folic acid supplements until it is too late(McGovern et al 1997) It is estimated that in someparts of the UK up to half of all pregnancies areunplanned and for this reason the statutory fortificationof flour with folic acid has been debated in the UK

In a report from the Committee on Medical Aspectsof Food Policy (COMA) it was estimated that fortifica-tion of flour at a level of 240 microg per 100 g would reducethe current level of NTDs by 41 without leading tounacceptably high intakes in other groups of the popu-lation (DH 2000) However in 2002 the Board of theFSA decided not to proceed with fortification primarilydue to concerns about the possibility of masking vitaminB12 deficiency anaemia in the elderly population

The governmentrsquos Scientific Advisory Committee onNutrition (SACN) was subsequently asked to reconsiderthe issue and has recently published a draft report onfolate and disease prevention (SACN 2005) There isnow evidence from countries that have introduced for-tification policies such as the USA and Canada that for-tification of flour can reduce the incidence of NTDs byaround 27ndash50 The report reaffirms the conclusionfrom the earlier COMA report that there is a need on

Table 5 The folatefolic acid content of a range of foods (per 100 g and per portion)

Food Amount (microg) per 100 g Amount (microg) per portion

Cereals amp cereal productsYeast extract 2620 26 (portion thinly spread on bread)Fortified breakfast cereals 111ndash333 33ndash100 (30 g portion)Granary bread 88 32 (medium slice)

FruitRaspberries raw 33 20 (60 g)Oranges 31 50 (medium orange)Orange juice 18 29 (160 ml glass)

VegetablesAsparagus boiled 173 216 (5 spears)Spring greens boiled 66 63 (95 g portion)Broccoli boiled 64 54 (85 g portion)Peas frozen boiled 47 33 (70 g portion)Lentils red dried boiled 33 13 (1 tablespoon)

Other foodsBeef mince cooked 17 24 (140 g portion)Milk semi-skimmed 9 23 (250 ml glass)Peanuts 110 14 (10 nuts)

Source McCance and Widdowsonrsquos The Composition of Foods (FSA 2002a)



balance for the introduction of mandatory fortificationof flour with folic acid in the UK (SACN 2005)

55 Key points

bull It is recommended that women who are considering apregnancy should try to achieve a healthy bodyweight(BMI of 20ndash25) as being either underweight or over-weight can affect both fertility and birth outcomebull Pre-pregnancy nutritional status is an importantdeterminant of fetal growth and development andtherefore a healthy and varied diet is important forwomen planning a pregnancy Certain food safety rec-ommendations should also be followed (see section 7)bull It is now well established that taking a folic acid sup-plement prior to conception and during the first12 weeks of pregnancy helps prevent the occurrence ofNTDs such as spina bifida

6 Nutritional requirements during pregnancy

It is now recognised that pregnant women do not actu-ally have to lsquoeat for tworsquo however a healthy and varieddiet which is rich in nutrients is important for both themother and the baby The developing fetus obtains all ofits nutrients through the placenta so dietary intake hasto meet the needs of the mother as well as the productsof conception and enable the mother to lay down storesof nutrients required for the development of the fetusand lactation after the birth

The healthy eating guidelines for pregnant women areactually very similar to those for non-pregnant womenwith a few exceptions The main recommendation is toeat a healthy balanced diet based on the Balance ofGood Health model which includes plenty of starchy

carbohydrates such as bread rice pasta and potatoesand is rich in fruit and vegetables A healthy dietincludes moderate amounts of dairy foods and protein-containing foods eg lean meat fish eggs and pulses(beans and lentils) and limited amounts of foods high infat or sugar

Changes in metabolism leading to more efficient util-isation and absorption of nutrients occur during preg-nancy which means that for many nutrients such ascalcium an increase in dietary intake over and abovethat which is normally required is not necessary Forsome nutrients however an increase in intake is recom-mended The UK COMA panel has set specific Refer-ence Nutrient Intakes (RNIs)1 for pregnancy Table 6shows the nutrients for which an increase in require-ment has been established

So far there have been very few dietary surveys thathave focused on nutrient intakes in pregnant women inthe UK However the Avon Longitudinal Study ofPregnancy and Childhood (ALSPAC) collected data onthe diets of almost 12 000 women at 32 weeks ofgestation using a food frequency questionnaire (FFQ)The data suggested that nutrient intakes in UK pregnantwomen are sufficient with the exceptions of iron mag-nesium and folate (Rogers amp Emmett 1998)

The recent National Diet and Nutrition Survey(NDNS) of adults aged 19ndash64 years indicates that a pro-portion of women of childbearing age have low intakesof several vitamins and minerals in particular vitaminA riboflavin iron calcium magnesium potassium andiodine (Henderson et al 2003b) Table 7 shows the per-

Table 6 Extra energy and nutrient requirements during pregnancy

Non-pregnant women (19ndash50 years) Extra requirement for pregnancy Comments

Energy (kcal) 1940 +200 Last trimesterProtein (g) 45 +6Thiamin (B1) (mg) 08 +01 Last trimesterRiboflavin (B2) (mg) 11 +03Folate (microg) 200 +100Vitamin C (mg) 40 +10 Last trimesterVitamin A (microg) 600 +100Vitamin D (microg) No RNI 10

Source DH (1991)Pregnant women are also advised to take a 400 microgday supplement of folic acid prior to and until the 12th week of pregnancy (more if there is a history of NTDs)NTDs neural tube defects RNI Reference Nutrient Intake

1The Reference Nutrient Intake (RNI) for protein or a vitamin or min-eral is the amount of nutrient that is enough or more than enough for about 975 of people in a group

42 C S Williamson


centage of women with intake from all sources (foodand supplements) below the Lower Reference NutrientIntake (LRNI)2 for selected nutrients

These data indicate that many women of childbearingage are not meeting their nutrient requirements and thisclearly has implications for pregnancy However lowintakes of some nutrients may be partly attributable tolow energy intakes or to underreporting which is acommon problem in dietary surveys The nutrients ofparticular concern are those for which there is anincreased requirement during pregnancy (vitamin Ariboflavin and folate) as well as iron and these are dis-cussed in more detail later in this section

Much of the following discussion is based on the rec-ommendations of the report of the Panel on DietaryReference Values (DRVs) of the Committee on MedicalAspects of Food Policy (DH 1991)

61 Energy

The maternal diet during pregnancy must provide suffi-cient energy to ensure the delivery of a full-term healthyinfant of adequate size and appropriate body composi-tion Ideally a woman should enter pregnancy with ahealthy weight and good nutritional status The addi-tional energy requirements of pregnancy therefore resultfrom the following (Goldberg 2002)

bull the need to deposit energy in the form of new tissuethis includes the fetus placenta and amniotic fluid

bull the growth of existing maternal tissues includingbreast and uterusbull extra maternal fat depositionbull increased energy requirements for tissue synthesisbull increased oxygen consumption by maternal organsbull the energy needs of the products of conception (fetusand placenta) particularly in the later stages ofpregnancy

Some of the energy costs of pregnancy are thought to bemet by a reduction in energy expenditure as women areassumed to become more sedentary during pregnancyHowever this is not the case for all individuals Somewomen may even become more active during pregnancyfor example if they go on maternity leave from a seden-tary job In addition general physical activity requiresmore energy during pregnancy due to an overall increasein body mass ie women tend to expend more energycarrying out the same activities Even within a particularsociety there is a wide variation in weight gain andenergy expenditure during pregnancy and therefore inenergy requirements

A joint FAOWHOUNU Expert Consultation onHuman Energy Requirements was held in 2001 and therecently published report reviews the recommendationsof the preceding consultation (held in 1981) The totalenergy cost of pregnancy has now been estimated ataround 321 MJ (77 000 kcal) This is based on datafrom longitudinal studies and factorial calculations ofthe extra energy required during this period (FAOWHOUNU 2004)

The consultation reviewed data from a number oflongitudinal studies carried out in healthy well-nour-ished groups of women with favourable pregnancy out-comes in order to calculate the extra energy requiredduring pregnancy This was calculated based on a meangestational weight gain of 12 kg with two factorialapproaches using either the cumulative increment inbasal metabolic rate (BMR) or the cumulative incre-ment in total energy expenditure (TEE) during preg-nancy in addition to the energy deposited as proteinand fat

It has previously been suggested that the energyrequirements of pregnant women should as with otheradult groups be based on multiples of BMR to takeinto account physical activity levels as women do notnecessarily reduce their energy expenditure during preg-nancy (Prentice et al 1996) Several studies have mea-sured BMR at different stages of pregnancy From thesestudies an average increase in BMR of 154 MJ through-out the gestational period was determined For each tri-mester the average increases in BMR were around 5

Table 7 Percentages of women with mean daily nutrient intakes (from all sources) below the LRNI2 for selected nutrients

Nutrient 19ndash24 years () 25ndash34 years () 35ndash49 years ()

Vitamin A 15 10 6Riboflavin (B2) 13 10 5Vitamin B6 5 1 2Folate 3 2 1Total iron 40 40 25Calcium 8 6 6Magnesium 22 20 10Potassium 30 30 16Zinc 5 5 3Iodine 12 5 4

Source National Diet and Nutrition Survey of adults aged 19-64 years(Henderson et al 2003b)

2The Lower Reference Nutrient Intake (LRNI) for protein or a vitamin or mineral is the amount of nutrient that is enough for only the few people in a group (25) who have low needs The majority of indi-viduals need more



10 and 25 of pre-pregnancy BMR respectivelyhowever there is a wide range in individual variability

Longitudinal studies using doubly labelled water tech-niques in developed countries such as the UK Swedenand the USA have found an average increase in TEE of165 by the third trimester of pregnancy TEE wasshown to increase by around 1 6 and 17 duringthe first second and third trimesters respectively whichis proportional to the increments in weight gain duringeach trimester For an average weight gain of 12 kg theincrease in energy required would be 0085 035 and13 MJday (20 85 and 310 kcalday) for each trimester(Butte amp King 2002)

Table 8 shows the additional energy costs of preg-nancy in each trimester based on calculations usingincrements in TEE for women with an average gesta-tional weight gain of 12 kg The estimates made usingcalculations based on increases in BMR were in factvery similar By averaging the two types of factorial cal-culations the current estimate of 321 MJ (77 000 kcal)was calculated as the extra energy cost of pregnancy(FAOWHOUNU 2004)

As Table 8 indicates the additional energy require-ments are not distributed evenly throughout the dura-tion of pregnancy Again by averaging the two differentfactorial calculations the additional energy costs cometo 035 12 and 20 MJday (85 285 and 475 kcalday)respectively for each trimester The joint consultationrecommends that in order to achieve this extra energyintake practical advice would be to add the smallrequirement for the first trimester to the second trimes-ter This would therefore mean that an extra 15 MJday(360 kcalday) would be required during the second and20 MJday (475 kcalday) required during the final tri-mester (FAOWHOUNU 2004)

These values are based on average energy requirementscalculated from studies of healthy well-nourished groupsof women However the energy requirements of indi-vidual women during pregnancy vary widely and areinfluenced by many factors so it can be difficult to makeindividual recommendations

In the UK the current recommendations are some-what more conservative The DRV for energy intakeduring pregnancy is an extra 200 kcalday during thethird trimester only Women who are underweight at thestart of their pregnancy and women who do not reducetheir activity may require more than this amount (DH1991) However it is currently assumed that if maternalweight gain and fetal growth are adequate then mater-nal energy intake must be sufficient to meet individualrequirements (Goldberg 2002)

62 Protein

The total protein requirement during pregnancy hasbeen estimated to be approximately 925 g for a womangaining 125 kg and delivering an infant of 33 kg (Hyt-ten 1980) Protein is not gained at a constant rate therate at which protein is deposited increases as pregnancyprogresses Estimates for the first second third andfourth quarters are 064 184 476 and 610 g of pro-tein per day respectively (FAOWHOUNU 1985)However more recent estimates from longitudinal stud-ies of women in developed countries (eg UK USA) sug-gest protein gains in pregnancy may be lower in therange of 497 to 696 g for an average weight gain of12 kg (FAOWHOUNU 2004)

The joint FAOWHOUNU consultation determinedthat an average increase in protein intake of 6 g per daywas required during pregnancy This was based on thecalculated average gain of 925 g of protein plus 30 (2standard deviations of birthweight) to allow for theprotein gains of nearly all normal pregnant women Thefigures also had to be adjusted for the efficiency withwhich dietary protein is converted to fetal placental andmaternal tissues (FAOWHOUNU 1985) A new FAOconsultation on protein requirements is due to report in2006

In the UK the DRV for protein intake is in line withthe above recommendation at an extra 6 g of proteinper day throughout pregnancy to achieve a total intakeof 51 g per day This is based on calculations of the

Table 8 Energy cost of pregnancy estimated from increments in total energy expenditure and energy deposition

1st trimester(kJday)

2nd trimester(kJday)

3rd trimester(kJday)

Total energy cost

(MJ) (kcal)

Protein deposition 0 30 121 141 3 370Fat deposition 202 732 654 1448 34 600Total energy expenditure 85 350 1300 1614 38 560Total energy cost 287 1112 2075 3202 76 530

Source FAOWHOUNU (2004)

44 C S Williamson


additional protein required for the products of concep-tion and growth of maternal tissues assuming a birth-weight of 33 kg (DH 1991) The majority of women inthe UK consume more protein than this however so itis unlikely that most women need to increase their pro-tein intake According to the recent NDNS of adultsaverage protein intake is 60 g per day in women aged19ndash24 years and 59 g per day in women aged 25ndash34 years (Henderson et al 2003c)

63 Fat

The DRV panel did not give any specific values for addi-tional fat requirements during pregnancy (DH 1991)However pregnant women and those planning a preg-nancy need an adequate dietary intake of essential fattyacids and their longer-chain derivatives DHA and AAwhich are necessary for the development of the brainand nervous system of the fetus particularly in latepregnancy (BNF 1999) The best dietary source of long-chain n-3 fatty acids (EPA and DHA) is oil-rich fishThere is also some evidence that an increased intake oflong-chain n-3 fatty acids during pregnancy may havebeneficial effects on birthweight or the duration of preg-nancy (eg Allen amp Harris 2001) See section 4 for amore detailed discussion on essential fatty acid require-ments during pregnancy

64 Carbohydrate

Requirements for starch sugar and non-starch polysac-charides (dietary fibre) during pregnancy are notincreased However constipation which may be partyattributed to reduced motility of the gastrointestinaltract is common at all stages of pregnancy Women withlow intakes of non-starch polysaccharides may benefitfrom increased intakes to within a range of 12ndash24 g perday along with increased fluid intakes to encourage reg-ular bowel movement (see section 82)

65 Vitamins

The DRV panel established DRVs for nine vitamins withincrements during pregnancy for vitamins A C and Dthiamin riboflavin and folate These are discussed below

651 Vitamin A

Extra vitamin A is required during pregnancy forgrowth and maintenance of the fetus for fetal stores ofvitamin A and for maternal tissue growth Requirementsare highest during the third trimester when fetal growthis most rapid The DRV panel concluded that vitamin A

intakes should be increased throughout pregnancy by100 microg per day (to 700 microg per day) This is to allow foradequate maternal storage so that vitamin A is availableto the fetus during late pregnancy

The recent NDNS of adults indicates that somewomen particularly those in the younger age groupshave an intake of vitamin A below the LRNI (seeTable 7) (Henderson et al 2003b) However if taken inexcessive amounts retinol is teratogenic and thereforepregnant women are advised to avoid liver and liverproducts and supplements containing retinol [unlessadvised otherwise by a general practitioner (GP)] Otherdietary sources of vitamin A and beta-carotene (egdairy products eggs carrots and leafy vegetables) canbe included as part of a healthy balanced diet duringpregnancy See section 71 for further details on foodsafety issues relating to vitamin A

652 Thiamin riboflavin and folate

Thiamin (B1) and riboflavin (B2) are needed for therelease of energy in the bodyrsquos cells Requirements forthiamin parallel the requirements for energy and aresubsequently higher for the last trimester of pregnancy(an increase of 01 mg to a total of 09 mg per day dur-ing the last trimester) The increment for average ribo-flavin intake is 03 mg per day (to a total of 14 mg perday) throughout pregnancy Note that an adaptiveresponse to pregnancy is reduced urinary excretion ofsome nutrients including riboflavin helping to meet theincreased demand

The latest NDNS of adults indicates that a significantproportion of women of childbearing age have intakesof riboflavin below the LRNI (see Table 7) Pregnantwomen should therefore be encouraged to consumeplenty of riboflavin-containing foods The main sourcesof riboflavin in the UK diet are milk and milk productscereals and cereal products (mainly fortified breakfastcereals) and meat and meat products (Henderson et al2003b) Good sources of riboflavin include milk anddairy products meat green leafy vegetables fortifiedbreakfast cereals yeast extract and liver however liverand liver products should be avoided during pregnancy(see section 71)

In addition to the recommendation to take a folic acidsupplement prior to conception and in the early stagesof pregnancy extra folate is also needed throughoutpregnancy in order to prevent megaloblastic anaemiaAn increment of 100 microg per day (to a total of 300 microg perday) was set by the DRV panel for the duration of preg-nancy This level of intake can be attained with a well-balanced diet which includes plenty of folate-rich foods



and foods fortified with folic acid (see Table 5) there-fore folic acid supplements are only recommended up tothe 12th week of pregnancy (see also section 54)

653 Vitamin C

The increment in vitamin C intake of 10 mg per day (toa total of 50 mg per day) during the last trimester ofpregnancy is to ensure that maternal stores are main-tained particularly towards the final stages of preg-nancy The rapidly growing fetus places a moderateextra drain on tissue stores as it is able to concentratethe vitamin at the expense of circulating vitamin levelsand maternal stores

Vitamin C also has an important role in enhancing theabsorption of non-haem sources of iron Pregnantwomen are therefore encouraged to consume foods ordrinks containing vitamin C together with iron-richmeals in order to help with iron absorption (FSA 2005b)

654 Vitamin D

The vitamin D status of adult women is maintainedmore by exposure to sunlight than through diet andthere is currently no RNI for vitamin D for adults under65 years Some vitamin D is available naturally in foodsincluding eggs meat and oil-rich fish Margarine is for-tified with vitamin D by law and it is also added to mostfat spreads and some breakfast cereals

Vitamin D is important for the absorption and utili-sation of calcium needed for the calcification of the fetalskeleton particularly during the later stages of preg-nancy and low vitamin D status can be detrimental toboth the mother and the fetus A recent study foundpoor maternal vitamin D status to be associated withreduced bone mass in the offspring (at age 9) and mayalso increase the risk of osteoporosis in later life (seeJavaid et al 2006) Pregnant women therefore need agood supply of vitamin D and supplements of 10 microg perday are currently recommended for all pregnant women(FSA 2005b)

A high prevalence of vitamin D deficiency has beenreported among Asian pregnant women in the UK par-ticularly among those who are vegetarian (Iqbal et al1994) It is thought that the rate of vitamin D synthesisin the skin may be slower in Asians than in caucasiansincreasing the need for dietary and supplemental vita-min D Women who receive little sunlight exposuresuch as those that cover up their skin when outdoorsare also likely to have low vitamin D status so it is par-ticularly important that they receive supplementary vita-min D during pregnancy

66 Minerals

The DRV panel established DRVs for 10 minerals (DH1991) however no increments were established forpregnancy as requirements are not considered toincrease This is mainly because of the more efficientabsorption and utilisation of nutrients that occurs dur-ing pregnancy

661 Calcium

The RNI for calcium for all adults is 700 mg per dayand the DRV panel did not consider that any incrementwas necessary during pregnancy Babies born at full-term contain approximately 20ndash30 g of calcium mostof which is laid down during the last trimester Althoughcalcium demands on the mother are high particularlyduring the latter stages of pregnancy physiologicaladaptations take place to enable more efficient uptakeand utilisation of calcium so an increased intake fromthe diet is not usually necessary These adaptationsinclude

bull An increase in the concentration of maternal free125-dihydroxyvitamin D3 (synthesised by the placenta)resulting in more efficient calcium absorptionbull Increased absorption may be stimulated by the hor-mones oestrogen lactogen and prolactinbull Enhanced calcium retention due to an increase inreabsorption in the kidney tubulesbull There is evidence that maternal bone density dimin-ishes during the first 3 months of pregnancy to providean internal calcium reservoir which is replenished by thelater stages of pregnancy

The DRV panel did however caution that higher mater-nal calcium intakes would be advisable in adolescentpregnancies Demineralisation of maternal bone may bedetrimental in adolescence when the skeleton is stillincreasing in density Furthermore any rapid maternalgrowth spurt may further deplete existing calciumstores Also if calcium intakes were low during child-hood and early adolescence calcium stores may beinsufficient to optimally meet both maternal and fetalneeds The RNI for calcium for girls aged 15ndash18 years isgreater than that of adults at 800 mg per day (see alsosection 92)

Other groups that may have inadequate calciumintakes include

bull women who consume little or no milk or dairyproductsbull vegan women

46 C S Williamson


bull Asian women who may have a low vitamin D status(see previous section) and also consume a high-fibre dietwhich can inhibit the absorption of calcium

Such individuals would benefit from appropriatedietary advice to ensure that they obtain enough calciumthroughout pregnancy Good dietary sources of calciuminclude milk and dairy products green leafy vegetablesfish containing soft bones (eg canned pilchards andsardines) pulses and foods made with fortified flour(eg bread) Milk and dairy products are the best dietarysources of calcium as they have a high calcium contentand the bioavailability is also high Alternative dietarysources for vegans and women who do not consumedairy foods also include nuts dried fruit and fortifiedsoya milk and other soya products eg tofu (see alsosection 91)

662 Iron

Iron requirements are increased during pregnancy tosupply the growing fetus and placenta and for the pro-duction of increased numbers of maternal red blood cellsThe RNI for iron intake for adult women is 148 mg perday and the DRV panel did not establish any incrementduring pregnancy as extra iron requirements were con-sidered to be met through

bull cessation of menstrual lossesbull increased intestinal absorptionbull mobilisation of maternal iron stores

The fetus accumulates most of its iron during the lasttrimester of pregnancy and the iron needs of the fetusare met at the expense of maternal iron stores Anaemiaduring pregnancy can increase the risk of having a LBWbaby and the infant developing iron deficiency anaemia(IDA) during the first few years of life (Allen 2000) (seealso section 83) However it is rare that a baby is bornwith IDA unless it is premature and therefore has nothad enough time to accumulate enough iron during thelast trimester (Thomas 2001)

A large proportion of women of childbearing age inthe UK (up to 50) have low iron stores and aretherefore at an increased risk of anaemia should theybecome pregnant (Buttriss et al 2001) Furthermorethe recent NDNS of adults aged 19ndash64 years indicatesthat iron intakes in women in the UK have decreasedover the last 15 years Currently 42 of 19ndash24-year-old women and 41 of 25ndash34-year-old women have aniron intake (from food sources) below the LRNI of 8 mgper day (Henderson et al 2003b)

The FSA recommends that women should try to eatplenty of iron-rich foods during pregnancy (eg lean red

meat pulses dark green leafy vegetables bread and for-tified breakfast cereals) and also try to consume foodscontaining vitamin C at the same time in order toenhance non-haem iron absorption (FSA 2005b)

Those most at risk of iron deficiency during pregnancyinclude women having successive births women fromlower socio-economic groups and teenagers (see section92) Ideally poor iron status should be addressed priorto conception The COMA report does recognise that ifiron stores are inadequate at the start of pregnancy sup-plementation may be necessary (DH 1991) In practicemany women are prescribed iron supplements duringpregnancy and may also be given dietary advice to helpthem increase their iron intake

67 Key points

bull With a few exceptions the dietary recommendationsfor pregnant women are the same as for other adultsbull There is an increased requirement for energy proteinand several micronutrients during pregnancy includingthiamin riboflavin folate and vitamins A C and Dbull The energy costs of pregnancy have been estimated ataround 321 MJ (77 000 kcal) in a recent consultationby WHO but this is not spread evenly throughout preg-nancy Most of the extra energy requirement is duringthe second and third trimestersbull In the UK an extra 200 kcal of energy per day is rec-ommended during the third trimester only Howeverthis assumes a reduction in physical activity level andwomen who are underweight or who do not reduce theiractivity level may require morebull There is an increased requirement for folatethroughout pregnancy to help prevent megaloblasticanaemia In addition to the recommendation to takesupplemental folic acid until the 12th week it is advis-able to consume plenty of folate-rich foods throughoutpregnancybull Some groups of women in the UK are vulnerable tovitamin D deficiency and it is recommended that preg-nant women take a vitamin D supplement of 10 microg perday throughout pregnancy as a precautionary measurebull There is no increment in calcium requirements duringpregnancy as metabolic adaptations enable more effi-cient absorption and utilisation during this periodHowever certain groups such as teenagers requiremore as they are still growingbull A large proportion of young women in the UK havelow iron stores and therefore may be at risk of anaemiashould they become pregnant Furthermore iron intakesin the UK appear to be decreasing Pregnant women aretherefore advised to consume plenty of iron-rich foods



during pregnancy and in some cases iron supplementa-tion may be necessary

7 Food safety issues during pregnancy

Pregnant women are advised to pay particular attentionto food hygiene during pregnancy and also to avoid cer-tain foods in order to reduce the risk of exposure tosubstances that may be harmful to the developing fetusPotentially harmful substances include food pathogens(eg listeria and salmonella) and toxic food components[eg dioxins and polychlorinated biphenyls (PCBs)] aswell as alcohol and high doses of some dietary supple-ments (eg vitamin A)

71 Vitamin A

Dietary vitamin A is obtained in two forms as the pre-formed vitamin (retinol) which is found in some animalproducts such as dairy products liver and fish liver oilsand as vitamin A precursors in the form of caroteneswhich are found in many fruits and vegetables

It is well known that excessive intakes of vitamin Ain the form of retinol may be toxic to the developingfetus The Expert Group on Vitamins and Minerals(EVM) considered the teratogenic risks associated withretinol in their report on safe upper levels for vitaminsand minerals Vitamin A has been shown to be terato-genic (cause malformations in an embryo or fetus) inanimals and a number of epidemiological studies inhumans have indicated that exposure to high levels ofvitamin A during pregnancy may increase the risk ofbirth defects (EVM 2003) The dose threshold for pre-vention of birth defects is still unclear but the lowestsupplemental dose associated with teratogenic effects is3000 microg per day (Rothman et al 1995) This has beensuggested as the dose threshold for teratogenicity(EVM 2003)

There have recently been concerns about the highconcentrations of vitamin A present in animal liver Atypical 100 g portion has been found to contain13 000ndash40 000 microg of vitamin A which is over 18 timesthe RNI for pregnant women This is thought to be dueto retinol being added to animal foodstuffs to aid pro-ductivity reproduction and immune status

In the UK the FSA currently advises women who arepregnant or may become pregnant to limit their intakeof vitamin A in the form of retinol by avoiding liver andliver products (eg liver pacircteacute and liver sausage) Theyshould also avoid taking supplements containing retinol(including high dose multivitamins) and cod liver oilsupplements unless advised to do so by their GP (FSA

2005b) This reflects the previously published DH rec-ommendations (1990)

A healthy and varied diet should provide sufficientvitamin A in the UK population Other sources of vita-min A in the diet (eg dairy products fat spreads eggscarrots and leafy vegetables) do not pose any risk ofexcessive intakes and should be included as part of ahealthy balanced diet during pregnancy

72 Alcohol

Alcohol consumption in high amounts has been shownto affect reproduction in women influencing the abilityto conceive and the viability of conception (Goldberg2002) Furthermore heavy alcohol intake in early preg-nancy can have potentially damaging consequences onthe embryo Women who might become pregnant aretherefore advised to avoid excessive intakes of alcoholas any adverse effects on the fetus could occur beforepregnancy has been confirmed

Drinking heavily throughout pregnancy ie intakesof more than 80 g of alcohol per day (equivalent to 10units) is linked with an increased risk of fetal alcoholsyndrome (FAS) This is characterised by reduced birth-weight and length including a small head size and avariety of congenital abnormalities as well as a charac-teristic facial appearance Affected children can exhibitmental retardation and stunted physical growthalthough not all infants exhibit all the features of FAS(Beattie 1992)

The effects of FAS may be more severe where mater-nal nutritional deficiencies also exist which frequentlyoccurs with alcohol abuse Intake of B vitamins is oftenlow while requirements may be increased due to exces-sive alcohol consumption Serum concentrations of anti-oxidant vitamins are reduced by excessive alcoholintakes yet these nutrients are essential in protectingagainst alcohol-induced free radical damage in maternaland fetal tissues Alcohol also has a detrimental effect onthe absorption and utilisation of folate thus compound-ing the problem of inadequate peri-conceptual folateintakes in women who drink alcohol heavily

There is currently a lack of consensus opinion onwhat is a safe level of alcohol consumption during preg-nancy The Royal College of Obstetricians and Gynae-cologists (RCOG) concluded from a review of theevidence that consumption of more than 3 drinks perweek during the first trimester of pregnancy leads to anincreased risk of spontaneous abortion and intakesover 15 units per week may have a negative effect onbirthweight The review found no conclusive evidence ofany adverse effects of a level of intake below 15 units

48 C S Williamson


per week The RCOG advises women to be cautiousabout their alcohol consumption during pregnancy andto consume no more than one standard drink per day(RCOG 1999)

DH (1995) currently recommends that pregnantwomen and those who may become pregnant shoulddrink no more than 1ndash2 units of alcohol once or twicea week at any stage of pregnancy and should avoidbinge drinking One unit of alcohol is a small (125 ml)glass of wine half a pint of standard-strength beer lageror cider or a single pub measure (25 ml) of spirit

However in some countries (including the USA Can-ada and Australia) complete abstinence from alcohol isnow recommended during pregnancy (see Mukherjeeet al 2005) In any case many women develop a spon-taneous distaste for alcoholic drinks from earlypregnancy

73 Caffeine

The Committee on Toxicity of Chemicals in Food Con-sumer Products and the Environment (COT 2001) hasrecently reviewed the evidence on the reproductiveeffects of caffeine They considered a large number ofstudies both human and animal and including epidemi-ological studies in the review

A number of studies have shown an associationbetween maternal caffeine intakes during pregnancyand an increased risk of both LBW and spontaneousabortion However the research has not found a thresh-old of caffeine intakes above which there is a definiterisk to pregnancy This is partly because caffeine comesfrom a number of sources and different studies assumebeverages to contain different amounts of caffeine TheCommittee considered that there is plausible evidenceof an association between caffeine intakes above300 mg per day and LBW as well as spontaneous abor-

tion Further studies are required however in order toestablish whether or not there is a causal link betweencaffeine intake and increased risk The Committee alsonoted that it is possible that other constituents in coffeenot necessarily caffeine per se may pose a risk and alsothat coffee and tea are not the only sources of caffeinein the diet and may not be the main sources for allindividuals

The Committee considered that the results of otherstudies that have investigated potential links betweencaffeine consumption during pregnancy and pre-termbirth or adverse effects on the fetus are so far incon-clusive They concluded that there was no reliable evi-dence that moderate intakes of caffeine (below 300 mgday) are associated with premature birth or otheradverse effects on the fetus In addition the review con-cluded that caffeine consumption does not appear toaffect male fertility while research into its effects onfemale fertility is still inconclusive

The FSA currently advises that women who are preg-nant or intend to become pregnant should limit theircaffeine intake to 300 mg per day (around four cups ofcoffee) Caffeine is present in a variety of foods and bev-erages including cocoa colas energy drinks and choc-olate as well as tea and coffee Note that the caffeinecontent of beverages such as tea and coffee variesgreatly depending on brewing method brand andstrength Caffeine is also found in a number of prescrip-tion and over-the-counter medicines eg headache pillscold and flu remedies diuretics and stimulants (COT2001) Typical caffeine contents of several foods anddrinks are shown in Table 9

In reality as with alcohol many women spontane-ously reduce their consumption of caffeinated drinkssuch as coffee during pregnancy The FSA also advisespregnant women to check with their GP or other healthprofessional before taking cold and flu medicines asmany contain caffeine (FSA 2005b)

Table 9 Caffeine contents of commonly consumed beverages and food

Beverage or food Serving size Caffeine content

Instant coffee 190 ml cup Approximately 75 mgBrewed coffee (filter or percolated) 190 ml cup Approximately 100ndash115 mgDecaffeinated coffee (instant or brewed) 190 ml cup Approximately 4 mgTea 190 ml cup Approximately 50 mgDrinking chocolate 200 ml 11ndash82 mg when made up as per manufacturersrsquo instructionsEnergy drinks (containing either added caffeine or guarana) 250 ml 28ndash87 mgCola (regular and diet) 330 ml can 11ndash70 mgChocolate 50 g bar 55ndash355 mg

Source COT (2001)



74 Foodborne illness

The following food pathogens can cause potential harmto the developing fetus during pregnancy This informa-tion is also summarised in Table 10

741 Listeriosis

Listeriosis is a flu-like illness caused by the bacteria List-eria monocytogenes Although listeriosis is rare in theUK if it occurs during pregnancy it can cause miscar-riage stillbirth or severe illness in the newborn Preg-nant women are therefore advised to avoid foods inwhich high levels of the bacteria have sometimes beenfound This includes pacircte and soft cheeses which aremould-ripened eg Brie Camembert and blue-veinedcheeses Hard cheeses such as cheddar and other cheesesmade from pasteurised milk pose no risk including cot-tage cheese mozzarella and processed cheese spreads(DH 2005) Unpasteurised milk and unpasteurised milkproducts should also be avoided

Listeria bacteria are destroyed by heat and thereforeas with the general population pregnant women areadvised to re-heat ready-prepared meals thoroughlyparticularly if they contain poultry Ready-preparedmeals which will not be re-heated should also beavoided eg purchased salads quiches and cold meatpies It is also advisable to wash fruit and vegetablesvery thoroughly especially if they are to be eaten raw inorder to minimise risk

742 Salmonella

Salmonella is a major cause of food poisoning in the UKand in severe cases it may cause miscarriage or prema-ture labour in pregnant women (Thomas 2001) Salmo-nella poisoning is most likely to come from raw eggs or

undercooked poultry therefore pregnant women areadvised to avoid eating raw eggs or foods containingraw or partially cooked eggs eg home-made mayon-naise Eggs should be cooked until the white and yolkare solid All meat in particular poultry needs to bethoroughly cooked and pregnant women should takeparticular care when handling these foods Raw foodsshould be stored separately from cooked foods in thefridge (so that raw foods cannot drip on cooked foods)in order to avoid the risk of cross-contamination

743 Toxoplasmosis

Toxoplasmosis is a condition caused by the organismToxoplasma gongii which can be found in raw meatunpasteurised milk and cat faeces Infection in preg-nancy can in rare cases lead to severe abnormalities inthe fetus including blindness and mental retardation(Thomas 2001) Pregnant women are advised to avoidraw or undercooked meat and unpasteurised milk andmilk products (particularly goatrsquos milk) as a precautionIn addition they should avoid contact with soil or catlitter trays by wearing gloves when gardening or chang-ing cat litter Pregnant women should be particularlycautious about food hygiene if cats come into theirkitchen

744 Campylobacter

Campylobacter is a genus of pathogenic organismswhich are a common cause of food poisoning in the UKInfections during pregnancy have been associated withpremature birth spontaneous abortion and stillbirthsCommon sources of infection include poultry unpas-teurised milk untreated water domestic pets and soilAs with other sources of infection observing goodhygiene practices helps to reduce risk

Table 10 Summary of foodborne pathogens that can cause potential harm in pregnancy

Consequences of infection in pregnancy Foods to avoid Further comments

Listeriosis Can cause miscarriage stillbirth or severeillness in the newborn

Pacircteacute and mould-ripened soft cheeses eg Brie Camembert blue-veined cheeses unpasteurised milk and milk products

Destroyed by heat so re-heat ready-prepared meals thoroughly Wash fruit and vegetables well

Salmonella In severe cases may cause miscarriage orpremature labour

Raw eggs or foods containing raw or partiallycooked eggs eg home-made mayonnaise

Cook eggs until white and yolk are solid Cook all meat particularly poultry thoroughly

Toxoplasmosis In rare cases can lead to severe fetal abnormalities

Raw or undercooked meat unpasteurised milkand milk products

Avoid contact with soil or cat liver traysby wearing gloves

Campylobacter May cause premature birth spontaneousabortion or stillbirth

Raw or undercooked poultry unpasteurisedmilk and milk products

Domestic pets and soil can also be a source of infection

50 C S Williamson


75 Fish

The FSA issued new advice on oil-rich fish consumptionfor the general population in 2004 including specificadvice for certain groups such as pregnant women Thisnew advice was based on a joint report from the SACNand the COT which considered the risks and benefits offish consumption in particular oil-rich fish (SACN2004) The new advice recommends for the first timemaximum intakes of oil-rich fish for different groups ofthe population

The current advice for the general population is toconsume at least two portions of fish per week one ofwhich should be oil-rich (DH 1994) This recommenda-tion also applies to pregnant and breastfeeding women(and women who may become pregnant) but with alimit of no more than two portions of oil-rich fish perweek

The basis for these recommendations is that the con-sumption of fish particularly oil-rich fish confers sig-nificant health benefits in terms of a reduction in therisk of CVD This is thought to be due to the long-chainn-3 PUFAs found in fish levels of which are particularlyhigh in oil-rich fish In addition these long-chain fattyacids are required for the development of the centralnervous system in the fetus and young infant so areimportant for both pregnant and breastfeeding womenHowever the FSA has set a maximum limit on oil-richfish consumption due to the risk of exposure to pollut-ants such as dioxins and PCBs which have been foundin oil-rich fish These are persistent compounds that mayaccumulate over time in the body and could haveadverse health effects if consumed at high levels over along period of time

Pregnant women and those who may become preg-nant are also advised to avoid marlin shark and sword-fish due to the risk of exposure to methylmercury whichat high levels can be harmful to the developing nervoussystem of the fetus (see Theobald 2003) For the samereason the FSA also advises pregnant women to limittheir intake of tuna to no more than two portions offresh tuna per week or four medium-sized tins of tunaper week (FSA 2005b) Mercury in the form of meth-ylmercury is concentrated up the food chain and there-fore found in highest amounts in large predatory fishthe highest concentrations have been found in sharkmarlin and swordfish

76 Food allergy

Peanut allergy is increasing in children and is the causeof some concern as allergy to peanut protein can cause

anaphylaxis (BNF 2002) The cause of peanut allergy isstill unclear but the use of peanuts and peanut oil hasincreased in the British diet over the past few years andit has been suggested that exposure to peanuts at ayoung age may cause the allergy The use of skin prep-arations containing peanut oil has also been implicated(Lack et al 2003)

Infants whose parents have a history of allergic dis-ease are more likely to develop allergies themselves It isthought that in such infants sensitisation to foreign pro-teins that cross the placenta may occur during preg-nancy (or via breastmilk during lactation) and thereforeit has been suggested that maternal avoidance of poten-tially allergenic foods during pregnancy and lactationmay help prevent allergy in infants (Goldberg 2002)However the evidence that prenatal exposure leads tosubsequent development of food allergy is weak (BNF2002)

Unless there is a strong family history of allergic dis-ease there is currently no convincing evidence that avoid-ance of these foods during pregnancy is protective againstchildhood allergy even in high-risk infants (Goldberg2002) It has also been suggested that exposure to foreignproteins via the placenta is important in helping the babyto develop a tolerance to the many foreign proteins in theenvironment (BNF 2002) Furthermore any diet thatexcludes specific foods may be restrictive in terms ofnutrient intake and therefore should only be followedunder medical supervision (although avoiding peanuts isconsidered to be less restrictive than other diets egexcluding wheat or dairy)

Current advice is that if there is a strong family his-tory of atopic disease (ie if either parent or a previouschild has suffered from hay fever asthma eczema orother allergy) then it may be advisable to avoid peanutsor foods containing peanuts during pregnancy andwhile breastfeeding in order to reduce the risk of theinfant developing a peanut allergy Also in cases wherethere is a familial history of allergic disease peanuts andpeanut-containing foods should not be given to childrenbefore the age of 3 years (FSA 2002b)

77 Key points

bull Excessive intakes of vitamin A in the form of retinolare toxic to the developing fetus and may cause birthdefects therefore pregnant women or those who maybecome pregnant are advised to limit their intake ofvitamin A by avoiding liver and liver products and sup-plements containing retinolbull Alcohol consumption in high amounts can be poten-tially damaging to the developing embryo and may



cause fetal alcohol syndrome The DH advises pregnantwomen and those who may become pregnant to limittheir alcohol consumption to no more than 1ndash2 unitsonce or twice per weekbull High intakes of caffeine during pregnancy mayincrease the risk of LBW or miscarriage and there-fore pregnant women or those who may becomepregnant are advised to limit their intake of caffeineto 300 mg per daybull Pregnant women are advised to pay particular atten-tion to food hygiene and to avoid certain foods duringpregnancy in order to minimise the risk of food poison-ing from potentially harmful pathogens such as listeriaand salmonellabull Pregnant women and those who may become preg-nant are advised to consume no more than two portionsof oil-rich fish per week to avoid exposure to dioxinsand PCBs They should also avoid shark marlin andswordfish and limit their intake of tuna to preventexposure to methylmercury which can be harmful tothe developing fetusbull The incidence of peanut allergy in children is on theincrease however there is a lack of evidence that pre-natal exposure to peanuts causes the development ofpeanut allergy in infants Pregnant women are currentlyonly advised to avoid peanuts during pregnancy if thereis a strong family history of allergic disease

8 Diet-related conditions during pregnancy

81 Nausea and vomiting and changes in taste and appetite

Symptoms of morning sickness nausea and vomiting(particularly in the first trimester) are reported to occurin around half to three-quarters of pregnant women(Buttriss et al 2001) The causes of these symptoms areunknown but a variety of triggers have been docu-mented including smells of foods perfume and cigarettesmoke Eating small high-carbohydrate snacks at fre-quent intervals (eg 2ndash3 hourly) often provides reliefalthough the reasons for this are unclear

Changes in taste and appetite are also common inpregnancy Some women experience increases in appe-tite which may be caused by hormonal changes orbecause of the removal of energy substrates from mater-nal blood by the fetus The development of cravings oraversions to foods is also often reported with the mostcommon cravings being for dairy products and sweetfoods Common aversions include tea and coffee alco-hol fried foods and eggs and in later pregnancy sweetfoods (Thomas 2001) In practice women usually learn

quite quickly which foods to avoid and this is unlikelyto affect nutritional status as long as the overall diet isnutritionally balanced (Goldberg 2003)

Pica is a condition where non-food substances such assoap coal and chalk are craved and consumed The rea-sons for the development of this condition areunknown but there is no clear evidence that it has anylink with mineral deficiencies (Thomas 2001) The inci-dence of pica in the UK appears to have decreased inrecent years (Buttriss et al 2001)

82 Constipation

It is quite common for women to suffer from constipa-tion during pregnancy The causes are complex but areprobably due to physiological effects on gastrointestinalfunction caused by pregnancy as well as a decline inactivity and changes in the diet (Thomas 2001)

Pregnant women are advised to increase their intakeof fibre (particularly wholegrain cereals) drink plenty offluids and take gentle exercise in order to alleviate thecondition Other considerations include the use ofdietary bulking agents and changing the type of ironsupplement used as iron supplements may sometimesaggravate the symptoms of constipation

83 Anaemia

Anaemia can be defined as lsquoa reduction in the oxygen-carrying capacity of the blood which may be due to areduced number of red blood cells a low concentrationof haemoglobin (Hb) or a combination of bothrsquo (Lloydamp Lewis 1996) Anaemia in pregnancy affects both themother and the fetus In the mother it may lead tosymptoms such as breathing difficulties faintingfatigue tachycardia (excessive heartbeat rate) and pal-pitations It may also lead to reduced resistance to infec-tion and the risk of haemorrhage before or after thebirth In the fetus anaemia can cause intrauterinehypoxia (low oxygen levels) and growth retardationalthough the effects of anaemia can be difficult to sep-arate from other factors such as social class and smok-ing (Stables 2000)

Most cases of anaemia during pregnancy are causedby iron deficiency however it is also associated withfolate deficiency blood loss and inherited conditionssuch as sickle cell anaemia and thalassaemia (Schwartzamp Thurnau 1995) Iron deficiency is fairly common dur-ing pregnancy however haematological changes duringpregnancy which reflect haemodilution can make it dif-ficult to correctly diagnose The WHO criteria for diag-nosis of anaemia in pregnancy is Hb lt 11 gdl however

52 C S Williamson


in practice many doctors only investigate women withHb lt 10 or 105 gdl (Stables 2000)

Iron deficiency anaemia (IDA) in pregnancy is a riskfactor for pre-term delivery and subsequent LBW Thereis also increasing evidence that maternal iron deficiencyin pregnancy results in reduced fetal iron stores that maylast well into the first year of life This may lead to IDAin infancy which could have adverse consequences oninfant development (Allen 2000) IDA is usually treatedwith oral iron supplements but intramuscular injectionor intravenous infusion can also be given if necessary Inpractice many women are prescribed iron supplementsat some point during pregnancy even though IDA is dif-ficult to diagnose Iron supplements should be pre-scribed with caution however as they may cause sideeffects such as nausea and constipation

Folate deficiency in pregnancy can in severe caseslead to megaloblastic anaemia This is most likely tooccur in late pregnancy or the first few weeks after thebirth Folate deficiency may lead to pallor fatigue andgastrointestinal symptoms such as nausea vomiting anddiarrhoea Megaloblastic anaemia can usually be treatedwith folic acid supplementation of 5ndash15 mg of folic aciddaily (Stables 2000) however this should be consideredin relation to the current recommendation to take folicacid supplements until the 12th week of pregnancy toprotect against NTDs (see section 54)

84 Gestational diabetes

Gestational diabetes (GDM) is the most common met-abolic disorder of pregnancy and occurs in around 2of all pregnancies usually in the last trimester It is oftenasymptomatic and is diagnosed by abnormal blood glu-cose results usually after a glucose tolerance test Fol-lowing delivery glucose metabolism may return tonormal or may stay impaired and in some cases mater-nal type 2 diabetes can develop GDM is associated withan increased risk of perinatal morbidity and mortality(Stables 2000)

GDM is more common among women from Asia andthe Middle East and there is an increased incidence inoverweight and obese women as well as older womenand those from lower socio-economic groups GDMleads to an increased risk of complications for both themother and the fetus including macrosomia (birthweightgt45 kg) and a greater likelihood of difficulties duringlabour There is also an increased risk of developing type2 diabetes in both the mother and infant although therisk can be reduced by maintaining a healthy body-weight taking regular physical activity and following ahealthy balanced diet (see Dornhorst amp Rossi 1998)

If GDM is diagnosed during pregnancy treatment isaimed at controlling blood glucose levels with addi-tional fetal monitoring in order to try to decrease theincidence of macrosomia Dietary management is usu-ally sufficient but occasionally insulin is also necessaryThere is currently some controversy over the dietaryguidelines for the management of GDM and a lack ofgood-quality trials in this area The limited evidenceavailable indicates that dietary changes are effective inimproving maternal hyperglycaemia and reducing therisk of accelerated fetal growth Dietary recommenda-tions include consuming regular meals and snacks thatcontain higher levels of slowly digestible carbohydrateAs many women with GDM are overweight or obesethe diet must also avoid excessive weight gain whichcan further compromise pregnancy outcomes(Dornhorst amp Frost 2002)

85 Hypertensive disorders

Pregnancy-induced hypertension (PIH) is a commoncondition specific to pregnancy that mainly occurs afterthe 28th week of gestation and disappears after deliveryThis is sometimes confused with a condition known aspre-eclampsia which is more severe and is also associ-ated with the appearance of the protein albumin in theurine (in the absence of other causes eg renal diseaseor pre-existing hypertension) Pre-eclampsia usuallyoccurs towards the end of pregnancy and causes highblood pressure in the mother

The aetiology of pre-eclampsia is unknown but obe-sity appears to be a risk factor (OrsquoBrien et al 2003) Itis an inflammatory condition involving endothelial dys-function and it has been suggested that certain otherdietary factors may be linked A number of trials haveindicated that supplementation with antioxidants (egvitamins C and E) may reduce the risk of pre-eclampsiaalthough these trials are of variable quality (Rumboldet al 2005) There is also some evidence from ran-domised controlled trials that calcium supplementationduring pregnancy may help reduce the risk of pre-eclampsia (Bucher et al 1996) but not all trials haveshown an effect Further investigation is therefore neededinto whether this condition can be successfully treated orprevented with dietary changes or supplementation

86 Key points

bull Symptoms of morning sickness nausea and vomitingare commonly reported in pregnancy Changes in appe-tite and taste (eg cravings or aversions to foods) alsofrequently occur As long as the diet is balanced overall



such changes are unlikely to have any adverse effect onnutritional statusbull It is also common for women to suffer from consti-pation during pregnancy increasing fibre intake drink-ing plenty of fluids and taking gentle exercise can helpalleviate the conditionbull Anaemia in pregnancy has effects on both the motherand the fetus and may lead to a variety of symptoms Inmost cases it is caused by iron deficiency which is fairlycommon during pregnancy but can be difficult to diag-nose IDA is a risk factor for both LBW and pre-termdelivery and is usually treated with oral iron supple-mentationbull GDM is the most common metabolic disorder ofpregnancy occurring in around 2 of all cases GDM ismore common in certain ethnic groups and women whoare overweight or obese It can lead to an increased like-lihood of complications such as macrosomia andlabour difficulties Dietary management is usually suffi-cient in treating the condition but more research isneeded in this areabull Hypertensive disorders such as pre-eclampsia cansometimes occur towards the end of pregnancy Obesityis a risk factor for pre-eclampsia but there is some evi-dence that other dietary factors may be linked Researchis ongoing into whether supplementation during preg-nancy (eg with antioxidant vitamins or calcium) mayhelp prevent this condition

9 Issues for specific groups

91 Vegetarians and vegans

As has already been highlighted there is an increasedrequirement for energy protein and some micronutri-ents during pregnancy including thiamin riboflavinfolate and vitamins A C and D (DH 1991) Typi-cally a vegetarian or vegan diet can meet theincreased demand for energy and protein duringpregnancy but there may be problems in trying toachieve the recommended intake of some vitaminsand minerals especially for vegans due to dietaryrestrictions

The four main categories of vegetarianism are asfollows

lsquoPartialrsquo or lsquosemirsquo vegetarians consume plant anddairy foods as well as eggs and fish may consume poul-try but avoid other types of meat

Lacto-ovo-vegetarians consume plant and dairyfoods and eggs but avoid all meat and fish

Lacto-vegetarians consume plant and dairy foodsbut avoid all meat fish and eggs

Vegans consume only foods of plant origin andexclude all meat fish dairy foods eggs or any foodsmade from animal products such as gelatine and suet

A study conducted by Draper et al (1993) in non-pregnant vegetarians and vegans found that in partialvegetarians and lacto-ovo-vegetarians mean intakes ofmicronutrients met the UK RNI However in vegansintakes of riboflavin vitamin B12 calcium and iodinewere below the RNI This highlights the fact that veganwomen may be vulnerable to low intakes of someimportant nutrients during pregnancy and the need foradequate dietary planning during this time Vegetariansand vegans may also have low intakes of iron zinc andvitamin D as a result of excluding meat from the diet(Philips 2005)

Several studies have looked at associations betweenfollowing a vegetarian or vegan diet during pregnancyand birth outcome but the results of these studies arenot always consistent For example Drake et al (1998)found no difference in length of gestation birthweightbirth length or head circumference between the babiesof lacto-ovo-vegetarians fish-eaters and meat-eatersHowever Sanders (1995) found that white vegan moth-ers had lower birthweight babies compared with womenfrom the rest of the population

Reddy et al (1994) studied the birth outcomes ofpregnant vegetarian women of Asian backgrounds liv-ing in the UK and found that offspring born to thesemothers had a lower birthweight smaller head circum-ference and shorter body length than infants of whiteomnivores In addition duration of pregnancy wasshorter onset of labour earlier and emergency caesareansections were more common than in white caucasianwomen even after adjusting for confounding variablessuch as maternal age height and gestational age It hasbeen suggested that the lower birthweights seen in veg-etarian mothers may be attributable to poor nutritionalstatus due to an inadequate intake of iron folate orvitamin B12 but further research in this area is needed(Philips 2005)

The type of dietary advice that is applicable to vege-tarians and vegans during pregnancy depends to a cer-tain extent on the type of vegetarian or vegan dietfollowed However with regard to food safety pregnantvegetarians and vegans should adhere to the samedietary advice as that given to all pregnant women (seesection 7) Although vegetarian and vegan diets providethe potential for low intakes of certain nutrients duringpregnancy it should still be possible for vegetarians andvegans to meet all their nutrient requirements as long asthe nutrients absent due to the avoidance of dairy orfoods of animal origin are replaced by other sources or

54 C S Williamson


supplements (University of Sheffield 2004) Table 11lists suitable alternative food sources for nutrients thatmay be inadequate in some vegetarian and vegan dietsand that are important during pregnancy

92 Teenage pregnancy

The UK has one of the highest rates of teenage pregnancyin Europe although rates have declined slightly since1998 In England the current teenage conception rate is421 per 1000 girls aged 15ndash17 In 2003 there were

39 571 under 18 conceptions of which 46 led to legalabortion (Office for National Statistics 2005) In gen-eral studies have shown that teenage pregnancy is asso-ciated with lower gestational weight gain and anincreased risk of LBW PIH pre-term labour IDA andmaternal mortality (Felice et al 1999) However manystudies in developed countries have been criticised fornot controlling for factors such as pre-pregnancy BMIlength of gestation ethnicity alcohol intake and smok-ing which have been shown to be associated with therisk of LBW (Goldberg 2002)

Table 11 Vegetarian and vegan sources of selected nutrients

Nutrient Vegetarian or vegan sources Further comments

Riboflavin (B2) Dairy products eggs yeast extract wheat germ almonds soya beans tempeh fortified foods including breakfast cereals and soya milk mushrooms and seaweeds

Vitamin B12 Dairy products eggs fortified foods including yeast extractsoya milk textured soya protein and breakfast cereals

This vitamin only occurs naturally in foods of animal origin Although there is no increment in the RNI for pregnancy vegetarians and vegans need to ensure they receive adequate amounts from their diet Vegans and those who avoid animal products completely need to include a source of vitamin B12 in their diet either in supplement form or from fortified foods

Vitamin D Dairy products eggs fortified foods including margarine and other fat spreads breakfast cereals soya milk and other soya products

The main source of vitamin D is from the action of sunlight on the skin so exposure to lsquogentlersquo sunlight in the summer months (April to October) is important in maintaining vitamin D status Vitamin D supplements (10 microg per day) are recommended for all pregnant women

Calcium Milk and dairy products green leafy vegetables pulses soybeans and fortified foods eg bread and soya milk tofu nuts and dried fruit

Milk and dairy foods are the best dietary sources of calcium as they have a high calcium content and the bioavailability is also high

Iron Pulses dark green leafy vegetables and fortified foods including breads and fortified breakfast cereals dried fruit nuts and seeds

Iron from plant foods is in the non-haem form which is less bioavailable than the haem form found in animal foods The absorption of non-haem iron is enhanced by consuming foods containing vitamin C at the same time as iron-containing foods However absorption is inhibited by tannins (in tea) phytates (in cereals and pulses) and fibre

Iodine Iodised salt milk and seaweeds The level of iodine found in plant foods varies depending on how much iodine is present in the soil where the plants are grown

Zinc Dairy products eggs bread and other cereal products pulses beans nuts seeds green vegetables and fortifiedbreakfast cereals

Vegetarian and vegan diets typically contain adequate amounts of zinc It is thought that adaptation to a vegetarian or vegan diet occurs over time resulting in increased absorption of zinc However zinc absorption is inhibited by phytates (in cereals and pulses) which are frequently associated with vegetarian and vegan diets

n-6 PUFAs Sources of linoleic acid include vegetable oils eg sunflower oil corn oil and soyabean oil and spreads made from these

Plasma levels of arachidonic acid (AA) have been found to be higher in vegetarians and vegans than omnivores and it is thought that sufficient AA can be synthesised from linoleic acid

n-3 PUFAs Sources of alpha-linolenic acid include linseed (or flaxseed)rapeseed oil walnut oil soyabean oil and blended vegetable oils tofu and walnuts

Conversion of alpha-linolenic acid to the long-chain n-3 fatty acids EPA and DHA is limited The only vegan sources of EPA and DHA are some seaweeds although algal supplements of DHA are now available

DHA docosahexaenoic acid EPA eicosapentaenoic acid PUFAs polyunsaturated fatty acids RNI Reference Nutrient Intake



The NDNS of young people aged 4ndash18 years foundthat a considerable percentage of adolescent girls hadnutrient intakes below the LRNI (Gregory et al 2000)Table 12 illustrates the percentage of girls aged 11ndash18 years with intakes below the LRNI for a range ofimportant nutrients (although these proportions may beslightly overestimated due to the problem of underre-porting) These data are also corroborated by serummeasurements which show that a high proportion ofteenage girls have poor iron folate and vitamin D status(Table 13)

Furthermore teenage pregnancy occurs at a timewhen the maternal body already requires extra nutrientsfor growth and development so there is potential com-petition for nutrients It is therefore possible that mater-nal growth and development may be compromised withpriority given to the developing fetus For this reason ahigher gestational weight gain is recommended for preg-nancy in adolescence in the USA (IOM 1990 Gutierrezamp King 1993) The availability of nutrients to the devel-oping fetus is an important factor in determining opti-mal birth outcome and it has also been suggested thatthere is a reduced flow of nutrients to the fetus in teen-age pregnancy due to immature placental development(Goldberg 2002)

One nutrient of particular importance during teenagepregnancy is calcium as a rapid increase in bone massoccurs during the adolescent years so the maternal skel-eton is still developing Although some physiologicaladaptations take place which help to meet additionalcalcium requirements during pregnancy teenage girlsrequire more calcium than adults for bone developmentThe RNI for calcium for girls aged 11ndash18 years is800 mg per day compared with 700 mg per day foradult women (DH 1991)

As indicated above iron intakes have been found tobe below the LRNI in up to half of teenage girls in theUK and many teenage girls have low iron stores(Tables 1213) This is attributed to low iron intakesbecause of a poor diet dieting to lose weight or vege-tarianism together with the demands of adolescentgrowth and the onset of menstruation Maternal IDA isa risk factor for pre-term delivery and subsequent LBW(see section 83) Therefore it is important to ensure anadequate intake of iron throughout pregnancy particu-larly in teenagers Iron supplements may also sometimesbe prescribed if necessary

Folate intake is a particular concern in teenage preg-nancies As already outlined inadequate folate intake isassociated with an increased risk of NTDs in the devel-oping fetus and therefore folic acid supplements are rec-ommended prior to conception and until the 12th weekof pregnancy This is often a problem in relation to teen-age pregnancies as around 75 are unplanned (Gold-berg 2002) Folic acid supplements are therefore oftennot taken prior to conception or in the early stages ofpregnancy either because pregnancy is undetected orbecause the importance of taking folic acid is not knownFurthermore menstruation is often irregular initially inteenage girls which compounds the problem of detect-ing pregnancy during the critical early stages whenfolate is important Also some teenage girls are preoc-cupied with their weight or may try to restrict weightgain in order to conceal the fact that they are pregnantResearch has also shown that dieting behaviour duringpregnancy including weight-loss diets fasting diets andeating disorders is associated with an increased risk ofNTDs (Carmichael et al 2003)

Adolescent pregnancy therefore presents many chal-lenges for health professionals and this section hashighlighted the importance of providing good dietaryadvice and support for teenagers who become pregnant

93 Dieting during pregnancy

For women with a normal pre-pregnancy BMI an aver-age weight gain of 12 kg (range 10ndash14 kg) during preg-

Table 12 Percentages of teenage girls with intakes below the lower reference nutrient intake (LRNI) for selected nutrients

Nutrient Girls aged 11ndash14 years () Girls aged 15ndash18 years ()

Vitamin A 20 12Riboflavin 22 21Folate 3 4Calcium 24 19Iron 45 50Zinc 37 10

Source National Diet and Nutrition Survey of young people aged 4-18 years(Gregory et al 2000)

Table 13 Percentages of teenage girls with poor nutrient status

ParameterGirls aged11ndash14 years ()

Girls aged15ndash18 years ()

Haemoglobin (lt12 gdl) 4 9Ferritin (lt15 gl) 14 27Red cell folate (lt350 nmoll) 11 14

(lt425 nmoll) 28 39Serum folate (lt63 nmoll) 1 1

(lt10 nmoll) 6 14Vitamin D (lt25 nmoll) 11 10


56 C S Williamson


nancy is associated with optimal maternal and fetaloutcomes This gain in weight is natural and should notbe avoided or minimised as low gestational weight gainis linked with poor fetal growth and development andan increased risk of having a LBW baby (Anderson2001 Buttriss et al 2001) In addition a low maternalweight gain is associated with an increased risk of pre-term delivery particularly for women who were under-weight or of an average weight before pregnancy(Schieve et al 2000 Mann amp Truswell 2002)

Studies looking at dieting behaviours includingrestricting food intake dieting to lose weight fastingdiets and eating disorders found this behaviour to beassociated with a higher risk of NTDs in the first tri-mester (Carmichael et al 2003) A study by Franko andSpurrell (2000) found that eating disorder behaviourduring pregnancy was also associated with higher ratesof miscarriage LBW and post-partum depressionAbraham (1994) studied the eating behaviour and atti-tudes to bodyweight of women who had recently givenbirth to their first child and found that women whoreported suffering from lsquodisordered eatingrsquo during preg-nancy were more likely to have given birth to a LBWinfant

Overall there is a consensus that dieting during preg-nancy should be discouraged (Anderson 2001) Preg-nancy is not a suitable time to restrict the diet or to loseweight as appropriate maternal weight gain is impor-tant for the mother as well as the fetus to ensure ade-quate fetal growth and development occurs

94 Key points

bull Vegetarians and vegans can have difficulty meetingtheir requirements for certain micronutrients duringpregnancy particularly riboflavin vitamin B12 calciumiron and zincbull Studies comparing birth outcomes (eg birthweightlength of gestation) in vegetarian or vegan mothersand omnivores have so far not produced consistentresultsbull Most vegetarian and vegan women should be able tomeet their nutrient requirements during pregnancy withcareful dietary planning However those on veryrestricted diets may also need to consume fortified foodsor supplementsbull Teenage pregnancy occurs at a time when the mater-nal body already has high nutrient requirements forgrowth and development and therefore there is poten-tial competition for nutrients Moreover a large propor-tion of teenage girls have low intakes of a range ofnutrients that are important during pregnancy

bull There are a number of nutrition-related problemsassociated with adolescent pregnancy including lowgestational weight gain and an increased risk of a num-ber of complications eg LBW and IDAbull The main nutrients of concern with regard to teenagepregnancy are calcium iron and folate In particularfolic acid supplements are often not taken prior to con-ception either because the pregnancy is unplanned orbecause teenagers are unaware of the importance of tak-ing folic acid Teenage pregnancy therefore presents par-ticular challenges for health professionalsbull Dieting during pregnancy has been associated with anincreased risk of NTDs and a number of other potentialcomplications An appropriate amount of weight gainduring pregnancy is important for fetal developmentand a healthy pregnancy outcome Pregnancy is there-fore not an appropriate time for dietary restriction anddieting should be strongly discouraged

10 Conclusions and recommendations

A healthy and varied diet that contains adequate amountsof energy and nutrients is essential for optimum fetalgrowth and development and to maintain good maternalhealth There is an increased requirement for energy pro-tein and several micronutrients during pregnancy How-ever in many women intakes of a range of nutrients arebelow the LRNI suggesting they are likely to be inade-quate In particular a high proportion of women of child-bearing age have low iron stores and intakes of iron havebeen declining over recent years The importance of gooddietary advice during pregnancy to encourage women toconsume a healthy balanced diet in particular plenty ofiron- and folate-rich foods should therefore not beunderestimated In addition a folic acid supplement(400 microgday) is recommended prior to and up to the12th week of pregnancy and a vitamin D supplement(10 microgday) is recommended throughout pregnancy

As well as following a healthy balanced diet stayingphysically active is also very important during preg-nancy Exercise can help prevent excess weight gain dur-ing pregnancy and help the mother return to a normalweight (BMI of 20ndash25) after the birth A number of tri-als have examined the effects of maternal exercise onfetal growth and pregnancy outcome although some areof poor quality However there is little evidence to sug-gest that regular moderate intensity exercise has anyadverse effects on the health of the mother or the infantStudies do suggest that regular aerobic exercise duringpregnancy helps improve or maintain physical fitnessand body image (Kramer 2002) It is recommended thatpregnant women should try to keep active on a daily



basis eg with regular walking Swimming is a suitableform of exercise and is particularly recommended dur-ing late pregnancy Strenuous physical activity should beavoided especially in hot weather and pregnant womenare advised to drink plenty of fluids to avoid becomingdehydrated (DH 2005)

Certain population groups may require closer atten-tion during pregnancy including teenage girls womenfrom certain ethnic groups and women from lowersocio-economic backgrounds In particular teenagepregnancy presents distinct nutritional challenges asteenagers are still growing and therefore there is poten-tial competition for nutrients between the mother anddeveloping fetus Moreover a large proportion of teen-age girls have low intakes of a number of importantnutrients and have been found to have poor iron folateand vitamin D status Folate intake is a particular con-cern as most teenage pregnancies are unplanned anddespite government campaigns only a small proportionof teenagers seem to be aware of the importance of tak-ing folic acid

There is now evidence from elsewhere in the worldthat mandatory fortification of flour with folic acid canlead to substantial reductions in the incidence of NTD-affected pregnancies and the governmentrsquos SACN hasrecently published a report recommending the introduc-tion of mandatory fortification of flour with folic acid inthe UK (SACN 2005) If this goes ahead it should helpaddress some of the problems of marginal folate statusin UK women and inadequate uptake of the folic acidrecommendations and ultimately help to reduce theincidence of NTD-affected pregnancies in the UK

Further information

For further practical information and advice on healthyeating during pregnancy see

The Food Standards Agency website httpwwweatwellgovuk

The Pregnancy Book March 2005 edition Available from the Department of Health website httpwwwdhgovuk

For further information on physical activity in preg-nancy see httpwwwbupacouk

References

Abraham S (1994) Attitudes to body weight weight gain and eating behaviour in pregnancy Journal of Psychosomatic Obstetrics and Gynecology 15 189ndash95

Al MDM van Houwelingen AC Kester ADM et al (1995) Maternal essential fatty acid patterns during normal pregnancy and its rela-tionship with the neonatal essential fatty acid status British Journal of Nutrition 74 55ndash68

Al MDM van Houwelingen AC amp Hornstra G (2000) Long-chain polyunsaturated fatty acids pregnancy and pregnancy outcome American Journal of Clinical Nutrition 71 (Suppl) 285ndash91

Allen LH (2000) Anemia and iron deficiency effects on pregnancy outcome American Journal of Clinical Nutrition 71 (Suppl) 1280ndash4

Allen KG amp Harris MA (2001) The role of n-3 fatty acids in gestation and parturition Experimental Biology and Medicine 226 498ndash506

Anderson AS (2001) Pregnancy as a time for dietary change Symposium on lsquoNutritional adaptation to pregnancy and lactationrsquo Proceedings of the Nutrition Society 60 497ndash504

Beattie JO (1992) Alcohol exposure and the fetus European Journal of Clinical Nutrition 46 (Suppl 1) 7ndash17

BNF (British Nutrition Foundation) (1999) n-3 Fatty Acids and Health BNF London

BNF (British Nutrition Foundation) (2002) Adverse Reactions to Food Report of a British Nutrition Foundation Task Force (J Buttriss ed) Blackwell Science Oxford

Bucher HC Guyatt GH Cook RJ et al (1996) Effect of calcium supplementation on pregnancy-induced hypertension and pre-eclampsia a meta-analysis of randomized controlled trials Journal of the American Medical Association 275 1113ndash17

Bull J Mulvihill C amp Quigley R (2003) Prevention of low birth weight assessing the effectiveness of smoking cessation and nutri-tional interventions Evidence briefing Health Development Agency July 2003 Available at httpwwwhda-onlineorguk

Butte N amp King JC (2002) Energy requirements during pregnancy and lactation Energy background paper prepared for the Joint FAOWHOUNU Consultation on Energy in Human Nutrition

Buttriss J (2004) Folate and folic acid an update for health professionals Available at httpwwwnutritionorguk

Buttriss J Wynne A amp Stanner S (2001) Nutrition A Handbook for Community Nurses Whurr Publishers London

Caan B Horgen DM Margen S et al (1987) Benefits associated with WIC supplemental feeding during the interpregnancy interval American Journal of Clinical Nutrition 45 29ndash41

Carmichael SL Shaw GM Schaffer DM et al (2003) Dieting behav-iour and risk of neural tube defects American Journal of Epidemi-ology 158 1127ndash31

Carr-Hill R Campbell DM Hall MH et al (1987) Is birthweight determined genetically British Medical Journal (Clin Res Ed) 295 687ndash9

Clark AM Thornley B Tomlinson L et al (1998) Weight loss in obese infertile women results in improvement in reproductive outcome for all forms of fertility treatment Human Reproduction 13 1502ndash5

COT (Committee on Toxicity of Chemicals in Food Consumer Prod-ucts and the Environment) (2001) Statement on the Reproductive Effects of Caffeine Available at httpwwwfoodgovuk

DH (Department of Health) Chief Medical Officer (1990) Depart-ment of Health Press Release No 90507 Women Cautioned Watch Your Vitamin A Intake Department of Health London

DH (Department of Health) (1991) Report on Health and Social Sub-jects No 41 Dietary Reference Values for Food Energy and Nutri-

58 C S Williamson


ents for the United Kingdom Report of the Committee on Medical Aspects of Food Policy HMSO London

DH (Department of Health) (1992) Folic acid the prevention of neural tube defects HMSO London

DH (Department of Health) (1994) Report on Health and Social Subjects No 48 Nutritional Aspects of Cardiovascular Disease Report of the Committee on Medical Aspects of Food Policy HMSO London

DH (Department of Health) (1995) Sensible Drinking The report of an inter-departmental working group Department of Health London

DH (Department of Health) (2000) Report on Health and Social Subjects No 50 Folic Acid and the Prevention of Disease 2000 Report of the Committee on Medical Aspects of Food Policy The Stationery Office London

DH (Department of Health) (2005) The Pregnancy Book March 2005 edition Available at httpwwwdhgovuk

Dornhorst A amp Frost G (2002) The principles of dietary management of gestational diabetes reflection on current evidence Journal of Human Nutrition and Dietetics 15 145ndash56

Dornhorst A amp Rossi M (1998) Risk and prevention of type 2 dia-betes in women with gestational diabetes Diabetes Care 21 (Suppl 1) B43ndashB49

Drake R Reddy S amp Davies G (1998) Nutrient intake during preg-nancy and pregnancy outcome of lacto-ovo-vegetarians fish-eaters and non-vegetarians Vegetarian Nutrition An International Jour-nal 2 45ndash50

Draper A Lewis J Malhotra N et al (1993) The energy and nutrient intakes of different types of vegetarians a case for supplements British Journal of Nutrition 69 3ndash19

EVM (Expert Group on Vitamins and Minerals) (2003) Safe Upper Levels for Vitamins and Minerals FSA London

Fall C (2005) Fetal and maternal nutrition In Cardiovascular Dis-ease Diet Nutrition and Emerging Risk Factors The Report of a British Nutrition Foundation Task Force (S Stanner ed) pp 177ndash95 Blackwell Science Oxford

FAOWHOUNU (1985) Report of a Joint Expert Consultation Energy and Protein Requirements Technical Report Series 724 WHO Geneva

FAOWHOUNU (2004) Report of a Joint FAOWHOUNU Expert Consultation Human Energy Requirements FAO Food and Nutri-tion Technical Paper Series No 1 2004

Felice ME Feinstein RA Fisher MM et al (1999) Adolescent preg-nancy ndash current trends and issues 1998 American Academy of Pedi-atrics Committee on Adolescence 1998ndash1999 Pediatrics 103 516ndash20

Franko DL amp Spurrell EB (2000) Detection and management of eating disorders during pregnancy Obstetrics and Gynaecology 95 942ndash6

FSA (Food Standards Agency) (2002a) McCance and Widdowsonrsquos The Composition of Foods Sixth summary edition Royal Society of Chemistry Cambridge

FSA (Food Standards Agency) (2002b) Feeding Your Baby Food Stan-dards Agency Publications London

FSA (Food Standards Agency) (2005a) Trying for a Baby (advice for women planning a pregnancy) Available at httpwwweatwellgovuk

FSA (Food Standards Agency) (2005b) When Yoursquore Pregnant (nutritional advice for pregnant women) Available at httpwwweatwellgovuk

Galtier-Dereure F Montpeyroux F Boulot P et al (1995) Weight excess before pregnancy complications and cost International Journal of Obesity 19 443ndash8

Godfrey KM amp Barker DJP (2000) Fetal nutrition and adult disease American Journal of Clinical Nutrition 71 (Suppl) 1344ndash52

Goldberg G (2002) Nutrition in pregnancy and lactation In Nutri-tion Through the Life Cycle (P Shetty ed) pp 63ndash90 Leatherhead Publishing Leatherhead UK

Goldberg G (2003) Nutrition in pregnancy the facts and fallacies Nursing Standard 17 39ndash42

Gregory J Lowe S Bates CJ et al (2000) The National Diet and Nutrition Survey Young People Aged 4ndash18 years The Stationery Office London

Gutierrez Y amp King JC (1993) Nutrition during teenage pregnancy Pediatric Annals 22 99ndash108

Henderson L Gregory J Irving K et al (2003a) The National Diet and Nutrition Survey Adults Aged 19ndash64 years Volume 4 Nutri-tional status (anthropometry and blood analytes) blood pressure and physical activity HMSO London

Henderson L Gregory J Irving K et al (2003b) The National Diet and Nutrition Survey Adults Aged 19ndash64 years Volume 3 Vitamin and mineral intake and urinary analytes HMSO London

Henderson L Gregory J Irving K et al (2003c) The National Diet and Nutrition Survey Adults Aged 19ndash64 years Volume 2 Energy protein carbohydrate fat and alcohol intake HMSO London

Hytten FE (1980) Nutrition In Clinical Physiology in Obstetrics (FE Hytten amp G Chamberlain eds) pp 163ndash92 Blackwell Publishing Oxford

Hytten FE amp Leitch I (1971) The Physiology of Human Pregnancy 2nd edn Blackwell Publishing Oxford

IOM (Institute of Medicine) Food and Nutrition Board (1990) Nutri-tion during Pregnancy National Academy Press Washington DC

Iqbal SJ Kaddam I Wassif W et al (1994) Continuing clinically severe vitamin D deficiency in Asians in the UK (Leicester) Postgraduate Medical Journal 70 708ndash14

Javaid MK Crozier SR Harvey NC et al (2006) Maternal vitamin D status during pregnancy and childhood bone mass at age 9 years a longitudinal study Lancet 367 36ndash43

Kramer MS (2002) Aerobic exercise for women during pregnancy (Cochrane review) Cochrane Database of Systematic Reviews (2) CD000180

Kramer MS Seguin L Lydon J et al (2000) Socio-economic dispari-ties in pregnancy outcome why do the poor fare so poorly Paedi-atric and Perinatal Epidemiology 14 194ndash210

Lack G Fox D Northstone K et al Avon Longitudinal Study of Par-ents and Children Study Team (2003) Factors associated with the development of peanut allergy in childhood New England Journal of Medicine 348 977ndash85

Lloyd C amp Lewis V (1996) Diseases associated with pregnancy In Myles Textbook for Midwives (VR Bennett amp IK Brown eds) 12th edn pp 333ndash64 Churchill Livingstone Edinburgh

Macfarlane A Mugford M Henderson J et al (2000) Birth Counts Statistics of Pregnancy and Childbirth Vol 2 The Stationery Office London

McGovern E Moss H Grewal G et al (1997) Factors affecting the use of folic acid supplements in pregnant women in Glasgow British Journal of General Practice 47 635ndash7



Makrides M amp Gibson RA (2000) Long-chain polyunsaturated fatty acid requirements during pregnancy and lactation American Jour-nal of Clinical Nutrition 71 (Suppl) 307Sndash11S

Mann J amp Truswell AS (2002) Essentials of Human Nutrition Oxford University Press Oxford

MRC Vitamin Study Research Group (1991) Prevention of neural tube defects results of the Medical Research Council Vitamin Study Lancet 338 131ndash7

Mukherjee RA Hollins S Abou-Saleh MT et al (2005) Low level alcohol consumption and the fetus British Medical Journal 330 375ndash6

Naismith DJ Rana SK amp Emery PW (1987) Metabolism of taurine during reproduction in women Human Nutrition Clinical Nutri-tion 41 37ndash45

OrsquoBrien TE Ray JG amp Chan WS (2003) Maternal body mass index and the risk of pre-eclampsia a systematic overview Epidemiology 14 368ndash74

Office for National Statistics (2005) Teenage Conception Statistics for England 1998ndash2003 In Health Statistics Quarterly Available at httpwwwdfesgovuk

Oken E Kleinman KP Olsen SF et al (2004) Associations of seafood and elongated n-3 fatty acid intake with fetal growth and length of gestation results from a US pregnancy cohort American Journal of Epidemiology 160 774ndash83

Olsen SF amp Secher NJ (2002) Low consumption of seafood in early pregnancy as a risk factor for preterm delivery prospective cohort study British Medical Journal 324 447ndash50

Philips F (2005) Briefing paper Vegetarian nutrition Nutrition Bul-letin 30 132ndash67

Prentice AM Spaaij CJ Goldberg GR et al (1996) Energy require-ments of pregnant and lactating women European Journal of Clin-ical Nutrition 50 (Suppl 1) 82ndash110

RCOG (Royal College of Obstetricians and Gynaecologists) (1999) Alcohol Consumption in Pregnancy RCOG London

Reddy S Sanders TAB amp Obeid O (1994) The influence of maternal vegetarian diet on essential fatty acid status of the newborn Euro-pean Journal of Clinical Nutrition 48 358ndash68

Rogers I amp Emmett P (1998) Diet during pregnancy in a population of pregnant women in South-West England European Journal of Clin-ical Nutrition 52 246ndash50

Rosello-Soberon ME Fuentes-Chaparro L amp Casanueva E (2005) Twin pregnancies eating for three Maternal nutrition update Nutrition Reviews 63 295ndash302

Rothenberg SP da Costa MP Sequeira JM et al (2004) Autoantibod-ies against folate receptors in women with a pregnancy complicated by a neural-tube defect New England Journal of Medicine 350 134ndash42

Rothman KJ Moore LL Singer MR et al (1995) Teratogenicity of high vitamin A intake New England Journal of Medicine 333 1369ndash73

Rumbold A Duley L Crowther C et al (2005) Antioxidants for pre-venting pre-eclampsia Cochrane Database Systematic Review (4) CD004227

SACN (Scientific Advisory Committee on Nutrition) (2004) Advice on fish consumption benefits and risks Available at httpwwwsacngovuk

SACN (Scientific Advisory Committee on Nutrition) (2005) Folate and Disease Prevention (Draft Report) Available at httpwwwsacngovuk

Sanders TAB (1995) Vegetarian diets and children Pediatric Nutrition 42 955ndash65

Schieve LA Cogswell ME Scanlon KS et al (2000) Prepregnancy body mass index and weight gain associations with preterm deliv-ery The NMIHS Collaborative Study Group Obstetrics and Gyne-cology 96 194ndash200

Schwartz WJ 3rd amp Thurnau GR (1995) Iron deficiency anaemia in pregnancy Clinical Obstetrics and Gynaecology 38 443ndash54

Smithells RW Sheppard S amp Schorah CJ (1976) Vitamin deficiencies and neural tube defects Archives of Disease in Childhood 51 944ndash50

Smithells RW Sheppard S Schorah CJ et al (1980) Possible preven-tion of neural-tube defects by periconceptional vitamin supplemen-tation Lancet 1 339ndash40

Smuts CM Huang M Mundy DA et al (2003) A randomised trial of docosahexaenoic acid supplementation during the third trimester of pregnancy Obstetrics and Gynecology 101 469ndash79

Sproston K amp Primatesta P (2003) Health Survey for England 2002 Volume 2 Maternal and Infant Health The Stationery Office London

Stables D (2000) Physiology in Childbearing with anatomy and related biosciences Harcourt Publishers Limited Edinburgh

Theobald H (2003) Oily fish and pregnancy Nutrition Bulletin 28 247ndash51

Thomas B (2001) Manual of Dietetic Practice 3rd edn Blackwell Publishing Oxford

Uauy R Peirano P Hoffman D et al (1996) Role of essential fatty acids in the function of the developing nervous system Lipids 31 S167ndashS176

UNICEFWHO (2004) Low Birthweight Country Regional and Glo-bal Estimates UNICEF New York Available at httpwwwwhointreproductive-healthpublicationslow_birthweight

University of Sheffield (2004) Healthy Eating Before During amp After Pregnancy Available at httpwwwshefacukpregnancy_nutrition

Wald NJ (2004) Folic acid and the prevention of neural tube defects New England Journal of Medicine 350 101ndash3

WHO (World Health Organization) (1995) Maternal anthropometry and pregnancy outcomes A WHO Collaborative Study World Health Organization Bulletin 73 (Suppl) 1ndash98

Zaadstra BM Seidell JC Van Noord PAH et al (1993) Fat and female fecundity prospective study of effect of body fat distribution on conception rates British Medical Journal 306 484ndash7


29


Nutrition Bulletin

31

28ndash59

7 FOOD SAFETY ISSUES DURING PREGNANCY

71 Vitamin A72 Alcohol73 Caffeine74 Foodborne illness741 Listeriosis742 Salmonella743 Toxoplasmosis744 Campylobacter75 Fish76 Food allergy77 Key points

8 DIET-RELATED CONDITIONS DURING PREGNANCY

81 Nausea and vomiting and changes in taste and appetite82 Constipation83 Anaemia84 Gestational diabetes85 Hypertensive disorders86 Key points

9 ISSUES FOR SPECIFIC GROUPS

91 Vegetarians and vegans92 Teenage pregnancy93 Dieting during pregnancy94 Key points

10 CONCLUSIONS AND RECOMMENDATIONSFURTHER INFORMATIONREFERENCES

Summary

A healthy and varied diet is important at all times in life but particularly so duringpregnancy The maternal diet must provide sufficient energy and nutrients to meetthe motherrsquos usual requirements as well as the needs of the growing fetus andenable the mother to lay down stores of nutrients required for fetal development aswell as for lactation The dietary recommendations for pregnant women are actu-ally very similar to those for other adults but with a few notable exceptions Themain recommendation is to follow a healthy balanced diet based on the

Balance ofGood Health

model In particular pregnant women should try to consume plenty ofiron- and folate-rich foods and a daily supplement of vitamin D (10

micro

gday) is rec-ommended throughout pregnancy

There are currently no official recommendations for weight gain during preg-nancy in the UK For women with a healthy pre-pregnancy weight an averageweight gain of 12 kg (range 10ndash14 kg) has been shown to be associated with thelowest risk of complications during pregnancy and labour and with a reduced riskof having a low birthweight (LBW) infant However in practice well-nourishedwomen with a normal pre-pregnancy bodyweight show wide variations in weightgain during pregnancy Low gestational weight gain increases the risk of having a

30

C S Williamson


Nutrition Bulletin

31

28ndash59



lt



micro




eg



eg



31


Nutrition Bulletin

31

28ndash59


eg



n-



12




eg


Keywords

birthweight

folic acid

food safety

oil-rich

fish

pregnancy

vitamin A

32

C S Williamson


Nutrition Bulletin

31

28ndash59

1 Introduction




eg


eg










Table 1










33


Nutrition Bulletin

31

28ndash59




et al



eg




et al







Table 2



2


lt


gt


gt

29

ge

6 kg


34

C S Williamson


Nutrition Bulletin

31

28ndash59




et al



24 Key points


eg






gt


lt



et al



et al




35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































30

C S Williamson


Nutrition Bulletin

31

28ndash59



lt



micro




eg



eg



31


Nutrition Bulletin

31

28ndash59


eg



n-



12




eg


Keywords

birthweight

folic acid

food safety

oil-rich

fish

pregnancy

vitamin A

32

C S Williamson


Nutrition Bulletin

31

28ndash59

1 Introduction




eg


eg










Table 1










33


Nutrition Bulletin

31

28ndash59




et al



eg




et al







Table 2



2


lt


gt


gt

29

ge

6 kg


34

C S Williamson


Nutrition Bulletin

31

28ndash59




et al



24 Key points


eg






gt


lt



et al



et al




35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson

















































































31


Nutrition Bulletin

31

28ndash59


eg



n-



12




eg


Keywords

birthweight

folic acid

food safety

oil-rich

fish

pregnancy

vitamin A

32

C S Williamson


Nutrition Bulletin

31

28ndash59

1 Introduction




eg


eg










Table 1










33


Nutrition Bulletin

31

28ndash59




et al



eg




et al







Table 2



2


lt


gt


gt

29

ge

6 kg


34

C S Williamson


Nutrition Bulletin

31

28ndash59




et al



24 Key points


eg






gt


lt



et al



et al




35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































32

C S Williamson


Nutrition Bulletin

31

28ndash59

1 Introduction




eg


eg










Table 1










33


Nutrition Bulletin

31

28ndash59




et al



eg




et al







Table 2



2


lt


gt


gt

29

ge

6 kg


34

C S Williamson


Nutrition Bulletin

31

28ndash59




et al



24 Key points


eg






gt


lt



et al



et al




35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson

















































































33


Nutrition Bulletin

31

28ndash59




et al



eg




et al







Table 2



2


lt


gt


gt

29

ge

6 kg


34

C S Williamson


Nutrition Bulletin

31

28ndash59




et al



24 Key points


eg






gt


lt



et al



et al




35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































34

C S Williamson


Nutrition Bulletin

31

28ndash59




et al



24 Key points


eg






gt


lt



et al



et al




35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson

















































































35


Nutrition Bulletin

31

28ndash59


et al


et al



et al

2003)



in utero






in utero



Table 3




SES groups


et al


36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































36

C S Williamson


Nutrition Bulletin

31

28ndash59


33 Key points


gt


lt




n-


n-



eg


The long-chain

n-


Figure 1

The

n-

6 and

n-




183 n-6 184 n-3

203 n-6 204 n-3


224 n-6 225 n-3


Table 4



















38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson



























































































38 C S Williamson


41 Key points





















54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson






















































































54 Folatefolic acid








40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































40 C S Williamson

















55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson



















































































55 Key points














42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































42 C S Williamson





61 Energy





















62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
























































































62 Protein








Total energy cost

(MJ) (kcal)



44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































44 C S Williamson



63 Fat


64 Carbohydrate


65 Vitamins


651 Vitamin A











653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson



















































































653 Vitamin C



654 Vitamin D




66 Minerals


661 Calcium






46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































46 C S Williamson




662 Iron








67 Key points







71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson





















































































71 Vitamin A







72 Alcohol





48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































48 C S Williamson





73 Caffeine










Source COT (2001)





741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson




















































































741 Listeriosis



742 Salmonella



743 Toxoplasmosis


744 Campylobacter
















50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































50 C S Williamson


75 Fish





76 Food allergy






77 Key points











82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson

























































































82 Constipation



83 Anaemia



52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson
















































































52 C S Williamson












86 Key points

















54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson































































































54 C S Williamson














































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson





































































































56 C S Williamson





94 Key points











Further information





References






















58 C S Williamson





















































































Further information





References






















58 C S Williamson
















































































58 C S Williamson
















































































nutrition in pregnancy - home - british nutrition foundation in pregnancy... · pregnancy are, in...

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