Journal of Obstetrics and Gynaecology (1999) Vol. 19, No. 5, 474± 476

OBSTETRICS

Obstetric hazards of maternal obesity

A. J. ROOPNARINESINGH, H. HOMER, B. BASSAW, A. SIRJUSINGH andS. ROOPNARINESINGHDepartment of Obstetrics and Gynaecology, University of the West Indies, Trinidad

Summary

To test the hypothesis that obesity represents a risk factor in

pregnancy, we conducted a prospective case± control study todetermine whether or not there was any divergence in the

obstetric outcome among 132 obese women from that in a

control group of 136 non-obese patients. Obese mothers hadan increased incidence of pregnancy-induced hypertension

and gestational diabetes but there was no signi® cant differ-ence in the duration of pregnancy or in the frequency of low

Apgar score at 1 minute. The favourable fetal outcome inobese parturients re¯ ects an increased awareness of the

possible medical and obstetric complications and an early

recourse to abdominal delivery.

IntroductionIn a previous analysis of our experience with obese

gravidae at this hospital, we reported a higher peri-

natal mortality rate and more depressed babies at birth

(Apgar score <7) than among non-obese mothers

(Naraynsingh et al., 1988). A policy of careful antenatal

surveillance for pregnancy-induced hypertension and

diabetes was instituted thereafter, and we adopted an

aggressive approach in favour of caesarean section

particularly for suspected fetal macrosomia.

The present investigation consists of a similar

appraisal of the reproductive performance of obese

parturients during the year 1997. The purpose of this

study was to establish whether or not there has been

any improvement in fetal outcome as a result of a

greater awareness of the major contributors to peri-

natal morbidity and mortality.

Patients and methodsOne hundred and thirty -two consecutive obese

pregnant patients were recruited from the antenatal

clinic of the Mount Hope Maternity Hospital which is

a tertiary care teaching institution. On the same day,

one or two controls were chosen from among the

antenatal clientele. None of these women had any

signi® cant pre-existing medical history at the booking

visit. The controls were matched for age, parity and

ethnicity. All patients were of low socioeconomic status.

Obesity was de® ned as a body mass index [weight

(kg)/height2

(m)] of ³ 30 at the ® rst antenatal visit. The

control group of 136 patients weighed between 50 and

65 kg with a body mass index of 20 ± 28.

All gravidae were routinely subjected to a 50 g oral

glucose screening test for diabetes, at least once in the

third trimester. Those with a plasma glucose value of

³ 140 mg/dl were further evaluated by a 75 g oral

glucose tolerance test.

Blood pressure was measured by the same observer

with the patient in a sitting position, using a mercury

sphygmomanometer and an appropriate-sized cuff.

Pregnancy-induced hypertension was de® ned as a blood

pressure of 140/90 mmHg or greater during the second

half of pregnancy in a previously normotensive woman.

If fetal macrosomia ( ³ 4000 g) was suspected on

abdominal palpation, caesarean section was embarked

upon, electively at 38 weeks or as an emergency, intra-

partum.

The antenatal course, gestational age at delivery,

mode of delivery and fetal outcome in terms of birth-

weight, Apgar scores and perinatal mortality were

documented.

Statistical analysis was employed using the c 2and

odds ratio (OR) and its 95% con® dence interval (CI).

A P value >0´05 was not considered signi® cant.

ResultsThe incidence of pregnancy-induced hypertension was

signi® cantly higher among obese patients (13´6% vs.

2´9%; P<0´01).

The incidence of diabetes among obese mothers was

higher than the control group but this difference was

not statistically signi® cant (11´4% vs. 6´5%; P>0´05).

There was no signi® cant difference in the incidence

of preterm ( £ 37 weeks) or post-term ( ³ 42 weeks)

deliveries between the obese and the control group

(Table I).

The caesarean section rate among obese patients

was almost twice that in the control group (26´5% vs.

14´7%; OR=1´8, 95% CI: 1´02± 3´28, P<0´05).

Obese mothers were delivered of more macrosomic

babies and fewer infants weighing less than 2500 g than

were non-obese mothers (Table II).

Table III reveals that the frequency of a low Apgar

score at 1 minute was similar in both groups (10´6% vs.

10´9%). Of the nine macrosomic infants in the obese

group, four were delivered by caesarean section with

zero mortality and of the ® ve delivered vaginally, one

developed shoulder dystocia and intrapartum asphyxia,

and died in the early neonatal period. The single

stillbirth in the obese group was an intrauterine demise

due to severe pre-eclampsia at 32 weeks. The perinatal

mortality rates in obese mothers and controls were

14/1000 and 6/1000, respectively. There were no

maternal deaths.

Correspondence to: Professor S. Roopnarinesingh, Mount Hope Women’s Hospital, Champs Fleurs, Trinidad.

ISSN 0144± 3615 print/ISSN 1364± 6893 online/99/050474± 03 � Institute of Obstetrics and Gynaecology Trust, 1999

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DiscussionThe medical-obstetric risk factors operating during the

antepartum period in obese pregnant patients have

remained unchanged over the past ® ve decades

(Douglas and Scadron, 1951; Tracy and Miller, 1969;

Roopnarinesingh and Pathak, 1970; Gross et al., 1980;

Konje et al., 1993). Our results verify that pregnancy-

induced hypertension is the principal medical complica-

tion in the obese mother (Kerr, 1962; Treharne, 1984).

Despite this ® nding, there is nothing we are currently

able to do as clinicians to prevent the development of

this disease. Imposition of caloric restrictions is not

recommended (Abrams, 1994) and how to manage this

disorder and achieve good perinatal outcome remains

a clinical challenge.

Previous correlations between maternal obesity and

gestational diabetes have been reported (Edwards et

al., 1978; Naraynsingh et al., 1988). The present study

reveals that although diabetes is more prevalent in obese

patients, the difference was not statistically significant.

This is probably due to the high prevalence of diabetes

in our native population (Poon King et al., 1968;

Bassaw et al., 1995). Seen in perspective, our analysis

suggests that one in nine obese mothers will develop

gestational diabetes whereas the frequency of diabetes

in pregnancy among the hospital population is one in

100 (Manjoo et al., 1987). These ® ndings reinforce the

view that maternal obesity is an important risk factor

in screening for gestational diabetes (Plante, 1998), a

disorder which can be treated adequately, in contrast

to pregnancy-induced hypertension.

With respect to the in¯ uence of obesity on birth-

weight, our results con® rm that obese parturients are

delivered of more macrosomic and fewer low birth-

weight babies than are non-obese mothers. That big

mothers tend to have big babies has been a consistent

observation in the past (Witten, 1958; Edwards et al.,

1978; Bromwich, 1986) and it has been speculated that

the obese mother may have an overriding metabolic

effect that overcomes the multiple risk factors for having

low birthweight infants (Gross et al., 1980). In view of

the potential dangers of vaginal delivery of large babies,

we consider it prudent to predict fetal size in all obese

patients before deciding on the mode of delivery.

However, correct identi® cation of a large baby has its

limitations, either by ultrasound (Tamura et al., 1986)

or clinically (Parks and Ziel, 1978; Svigos, 1981; Rose

and McCallum, 1987) and in obese mothers, this is

further compounded by the inherent difficulty in

palpating a fetus through a sea of fat. The present

study demonstrates this drawback since only four of

the nine macrosomic infants were identi® ed before birth

by external palpation.

In our study a decade ago, we reported a perinatal

mortality rate of 3´7% and a caesarean section rate of

16´7% in obese gravidae (Naraynsingh et al., 1988). In

the current investigation, these ® gures are 1´4% and

26´5%, respectively, suggesting an inverse relationship

between these two parameters. This observation gives

some logical support to the inference that appropriate

use of caesarean section will contribute to diminishing

perinatal mortality. The achievement of a favourable

fetal outcome despite the prevalence of diabetes and

hypertension corroborates an Australian report (Calan-

dra et al., 1981) but differs from the British and

Jamaican experience (Kerr, 1962; Roopnarinesingh and

Pathak, 1970, respectively). These uniformly excellent

results in Trinidad may well be due to the implementa-

tion of attentive antenatal care, routine screening for

diabetes and a low threshold for operative intervention

in obese pregnant patients.

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Table I. Gestational age at delivery

Gestational age (weeks) Obese group (n) Control group (n) P value

£ 37 10 (7´6%) 19 (13´9%) >0´05>37± <42 112 (84´9%) 107 (78´7%) >0´05³ 42 10 (7´6%) 10 (7´4%) >0´05

n indicates the number of patients.

Table II. Comparison of birthweight between obese mothers and controls

Birthweight (grams) Obese (n) Non-obese (n) P value

<2500 5 18 <0´05³ 2500± 3999 118 117 NS>4000 9 1 <0´001

n indicates the number of patients.

Table III. Fetal outcome in obese mothers and controls

Complication Obese group (n) Control group (n)

Apgar score <7 14 (10´6%) 17 (10´9%)Shoulder dystocia 1 0Stillbirth 1 1Neonatal death 1 0

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Obstetric hazards of maternal obesity 475J

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