gestational diabetes mellitus: prevalence, risk factors, maternal and infant outcomes

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Ž . International Journal of Gynecology & Obstetrics 75 2001 221228 Article Gestational diabetes mellitus: prevalence, risk factors, maternal and infant outcomes X. Xiong a, ,1 , L.D. Saunders b , F.L. Wang c , N.N. Demianczuk d a Department of Obstetrics and Gynecology, La al Uni ersity, Quebec City, Canada b Department of Public Health Sciences, Uni ersity of Alberta, Edmonton, Canada c Alberta Health and Wellness, Edmonton, Canada d Department of Obstetrics and Gynecology, Uni ersity of Alberta, Edmonton, Canada Received 26 March 2001; received in revised form 31 May 2001; accepted 8 August 2001 Abstract Objecti es: To study prevalence, risk factors, and maternal and infant outcomes of women with gestational diabetes Ž . mellitus GDM . Methods: A retrospective cohort study was performed based on 111 563 pregnancies delivered between 1991 through 1997 in 39 hospitals in northern and central Alberta, Canada. Multivariate logistic regression was used to estimate the odds ratios with 95% confidence intervals, and to control for confounding variables. Results: The prevalence of GDM was 2.5%. Risk factors for GDM included age 35 years, obesity, history of prior neonatal death, and prior cesarean section. Teenage mothers and women who drank alcohol were less likely to have GDM. Mothers with GDM were at increased risk of presenting with pre-eclampsia, premature rupture of membranes, cesarean section, and preterm delivery. Infants born to mothers with GDM were at higher risk of being macrosomic or large-for-gestational-age. Conclusions: Specific conditions predispose to GDM which itself is associated with a significantly increased risk of maternal and fetal morbidity. 2001 Elsevier Science B.V. International Federation of Gynecology and Obstetrics. Keywords: Birth outcome; Epidemiology; Gestational diabetes mellitus; Pregnancy; Prevalence Corresponding author. Hopital Saint-Franc ¸ ois d’Assise, Centre de recherche-D1-724, 10, rue de l’Espinay, Quebec, Canada, ˆ ´ G1L 3L5. Tel.: 1-418-525-4444 ext. 2419; fax: 1-418-525-4194. Ž . E-mail address: [email protected] X. Xiong . 1 At time of the study, Xu Xiong was with the Perinatal Research Centre, the Department of Obstetrics and Gynecology and the Department of Public Health Sciences of University of Alberta. 0020-729201$20.00 2001 International Federation of Gynecology and Obstetrics. All rights reserved. Ž . PII: S 0 0 2 0 - 7 2 9 2 01 00496-9

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Page 1: Gestational diabetes mellitus: prevalence, risk factors, maternal and infant outcomes

Ž .International Journal of Gynecology & Obstetrics 75 2001 221�228

Article

Gestational diabetes mellitus: prevalence, risk factors,maternal and infant outcomes

X. Xionga,� ,1, L.D. Saundersb, F.L. Wangc, N.N. Demianczukd

aDepartment of Obstetrics and Gynecology, La�al Uni�ersity, Quebec City, CanadabDepartment of Public Health Sciences, Uni�ersity of Alberta, Edmonton, Canada

cAlberta Health and Wellness, Edmonton, CanadadDepartment of Obstetrics and Gynecology, Uni�ersity of Alberta, Edmonton, Canada

Received 26 March 2001; received in revised form 31 May 2001; accepted 8 August 2001

Abstract

Objecti�es: To study prevalence, risk factors, and maternal and infant outcomes of women with gestational diabetesŽ .mellitus GDM . Methods: A retrospective cohort study was performed based on 111 563 pregnancies delivered

between 1991 through 1997 in 39 hospitals in northern and central Alberta, Canada. Multivariate logistic regressionwas used to estimate the odds ratios with 95% confidence intervals, and to control for confounding variables. Results:The prevalence of GDM was 2.5%. Risk factors for GDM included age �35 years, obesity, history of prior neonataldeath, and prior cesarean section. Teenage mothers and women who drank alcohol were less likely to have GDM.Mothers with GDM were at increased risk of presenting with pre-eclampsia, premature rupture of membranes,cesarean section, and preterm delivery. Infants born to mothers with GDM were at higher risk of being macrosomicor large-for-gestational-age. Conclusions: Specific conditions predispose to GDM which itself is associated with asignificantly increased risk of maternal and fetal morbidity. � 2001 Elsevier Science B.V. International Federation ofGynecology and Obstetrics.

Keywords: Birth outcome; Epidemiology; Gestational diabetes mellitus; Pregnancy; Prevalence

� Corresponding author. Hopital Saint-Francois d’Assise, Centre de recherche-D1-724, 10, rue de l’Espinay, Quebec, Canada,ˆ ´G1L 3L5. Tel.: �1-418-525-4444 ext. 2419; fax: �1-418-525-4194.

Ž .E-mail address: [email protected] X. Xiong .1 At time of the study, Xu Xiong was with the Perinatal Research Centre, the Department of Obstetrics and Gynecology and the

Department of Public Health Sciences of University of Alberta.

0020-7292�01�$20.00 � 2001 International Federation of Gynecology and Obstetrics. All rights reserved.Ž .PII: S 0 0 2 0 - 7 2 9 2 0 1 0 0 4 9 6 - 9

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1. Introduction

Controversies still exist regarding gestationalŽ .diabetes mellitus GDM and its prevalence,

screening, clinical management and impact on� �maternal and infant outcomes 1�5 . There is also

increasing debate on the benefit of the current� �universal screening of GDM 1�3 . GDM is not a

disease per se, but an abnormal laboratory plasma� �glucose value 2 . The increase in prevalence of

GDM is recently reported to be an artifact causedby universal screening, with no evidence of bene-fit of the universal screening to pregnancy out-

� �comes 3 . In order to evaluate the prevalenceand risk factors of GDM and its impact on mater-nal and infant outcomes in the population wherethe universal screening of GDM is applied, weconducted a retrospective cohort study of 111 419pregnancies delivered between 1991 and 1997 in39 hospitals in northern and central Alberta,Canada.

2. Methods

2.1. Study population

The data for the present study originate fromthe Northern and Central Alberta Perinatal Au-dit and Education Program. This program was

� �described in detail elsewhere 6,7 . Briefly, thisprogram initiated data collection in 1991 for thepurposes of monitoring obstetrical interventionsand to monitor the impact of educational strate-gies aimed at reducing the incidence of obstetricinterventions. The database is derived directlyfrom information reported on the standard laborand delivery record used in Alberta. The databaseincludes a total of 189 separate items relating to:demographic information, pre-pregnancy and pastobstetric history, smoking during pregnancy, al-cohol consumption and drug dependence, prob-lems in current pregnancy, intrapartum risk,obstetrical interventions and their indications, in-trapartum events and birth outcomes as well asneonatal data. Every effort is made to ensureaccuracy of the data at both the data supplier andPerinatal Audit level. Records from participating

hospitals received in paper format are reviewedby the Audit Coordinator to check for discrepan-cies before being entered into the database by adata clerk. The data validation is performed atthree levels: the registry is checked for missing orincomplete data, the computer program runscross-tabulations which reduce the risk of typingerrors and ongoing manual review of a randomsample of charts for accuracy of information. Aminimum of 1:20 records is verified with theactual data entry.

The computerized data from July 1, 1991, toDecember 31, 1997, were extracted for the pre-sent study. Data included in our study were col-lected from 39 hospitals and consisted of informa-tion pertaining to 117 375 pregnancies. We ex-cluded cases with pre-pregnancy diabetes con-

Ž .trolled by diet n�603 , pre-pregnancy diabetesŽ .controlled by insulin n�334 , diabetes compli-Ž .cated by retinopathy n�19 , cases without ante-

Ž .natal information n�2576 , and cases with in-Ž .consistent information n�2424 . After exclu-

sions, 111 419 pregnancies were left for analysis.This study was approved by the Health ResearchEthics Board of University of Alberta.

2.2. Definition of GDM and other co�ariates

In Alberta, pregnancies are universally screenedfor GDM between 24 and 28 weeks of gestation.The screening test used is a 50-g glucose load,given orally at any time of the day, with plasmaglucose measured 1 h later. If the 1-h value is 7.8mmol�l or greater, a glucose tolerance test isrequested. The glucose tolerance test is com-prised of plasma glucose determinations, the firstwhile fasting and subsequently at 1, 2 and 3 hafter ingesting a 100-g glucose load. GDM isdiagnosed when any two of these plasma glucose

Žvalues i.e. fasting �5.8 mmol�l, 1 h�10.5.mmol�l, 2 h �9.2 mmol�l, 3 h �8.0 mmol�l

� �were equal or greater 8 .Maternal smoking is defined as women who

smoke at anytime during pregnancy. Maternalalcohol consumption was recorded if the womenconsumed either � three drinks at any one occa-sion or � one drink per day during pregnancy.The maternal alcohol information was collected

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since the beginning of 1995. Maternal weight,categorized as �45 kg, 46�90 kg and �91 kg,was recorded since 1996. The relationship betweenmaternal alcohol consumption, maternal weightand GDM was analyzed on the basis of dataavailable. Gestational hypertension was definedas a recorded blood pressure equal to or greaterthan 140�90 mmHg on more than two occasionsgreater than 6 h apart without proteinuria afterthe 20th week of gestation. Pre-eclampsia wasdefined as a blood pressure of greater than 140�90mmHg with proteinuria of at least 1� or moreon a dipstick in two samples 6 h apart or greaterthan 0.3 g in a 24-h urine collection. The infant’s

Žoutcomes include preterm birth �37 weeks of. Ž .gestation , low birth weight �2500 g , macro-

Ž . Ž .somia �4200 g , small-for-gestational-age SGAdefined as birth weight below the tenth percentileof expected weight for gestational age, and large-

Ž .for-gestational-age LGA as birth weight greaterthan the ninetieth percentile of expected weightfor gestational age according to a Canadian birth

� �weight distribution plot 9 .

2.3. Statistical analysis

The rates were calculated for women with GDMand women without GDM for selected potentialrisk factors, and for maternal and infants’ out-

comes. Chi-square tests were performed to testŽ .statistical significance. Odds ratio OR and the

Ž .95% confidence intervals C.I. were calculated.Analysis of variance was used to compare thedifference in gestational age, birth weight andApgar scores between women with GDM and

� �women without GDM 10,11 . To assess the inde-pendent effect of each individual risk factor at-tribute to GDM and to evaluate the independenteffect of GDM on the maternal and infants’ out-comes, multivariate logistic regression was ap-

Ž .plied. The adjusted odds ratio aOR and the95% C.I. were derived from the coefficient of the

� �logistic model and its standard error 10,11 . AllP-values were two-tailed, and the significance levelselected was 0.05. All statistical analyses were

Žperformed using SPSS 8.0 for Windows SPSS Inc.,.Chicago, IL .

3. Results

Fig. 1 presents the prevalence of GDM innorthern and central Alberta from 1991 to 1997.The prevalence ranged between 2.2 and 2.8%,with an average rate of 2.5%. The test of linear

Žtrend was not statistical significant P �linear trend.0.05 .

Table 1 shows the demographic and reproduc-

Fig. 1. The prevalence of GDM from 1991 to 1997, Alberta, Canada.

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Table 1Demographic and reproductive characteristics of GDM, Alberta, Canada, 1991�1997

Characteristics Subjects Non-diabetes GDM Unadjusted OR Adjusted ORaŽ . Ž . Ž . Ž .N N�108 664 N�2755 95% C.I. 95% C.I.

Ž . Ž . Ž .% % %

ParityŽ .Nulliparous 44 772 40.4 40.5 37.3 � �

��Ž . Ž . Ž .Multiparous 65 973 59.6 59.5 62.7 1.15 1.06�1.24 0.90 0.82�1.04Ž .Maternal age years

�� ��Ž . Ž . Ž .�19 9193 8.4 8.5 2.6 0.34 0.27�0.43 0.35 0.27�0.44Ž .20�34 88 740 81.0 81.1 75.0 � �

�� ��Ž . Ž . Ž .�35 11 667 10.6 10.3 22.4 2.34 2.13�2.56 2.34 2.13�2.58bŽ .Maternal weight kg

Ž . Ž . Ž .�45 196 0.5 0.5 0.5 1.01 0.42�2.47 1.02 0.45�2.73Ž .46�90 35 427 91.9 92.1 83.8 � �

�� ��Ž . Ž . Ž . Ž .�91 obesity 2919 7.6 7.3 15.8 2.36 2.00�2.80 2.40 2.06�2.98Maternal smoking

Ž .No 82 220 73.2 73.1 76.3 � ���Ž . Ž . Ž .Yes 30 107 26.8 26.9 23.7 0.81 0.77�0.92 0.96 0.87�1.05

cAlcohol useŽ .No 56 299 98.0 98.0 99.3 � �

�� �Ž . Ž . Ž .Yes 1128 2.0 2.0 0.7 0.37 0.20�0.67 0.40 0.25�0.76History of neonatal death

Ž .No 111 566 99.3 99.4 98.7 � ��� ��Ž . Ž . Ž .Yes 754 0.7 0.6 1.3 2.09 1.50�2.92 1.19 1.06�1.34

History delivery �37 weeksŽ .No 108 407 96.5 96.6 95.7 � �

�Ž . Ž . Ž .Yes 3913 3.5 3.4 4.3 1.25 1.03�1.51 1.11 0.91�1.35History of cesarean section

Ž .No 100 850 89.8 89.9 85.2 � ��� ��Ž . Ž . Ž .Yes 11 469 10.2 10.1 14.8 1.55 1.39�1.72 1.18 1.11�1.25

History of major fetal anomalyŽ .No 110 657 99.3 99.3 99.0 � �

��Ž . Ž . Ž .Yes 742 0.7 0.7 1.0 1.49 1.02�2.20 1.09 0.73�1.64

OR, odds ratio; 95% C.I., 95% confidence interval. � P�0.05; �� P�0.01.a By controlling for all variables in this table.b Based on 38 542 pregnancies between 1996 and 1997.c Based on 57 427 pregnancies between 1995 and 1997.

tive characteristics of women with GDM. Univari-ate analysis suggested that GDM occurred morefrequently among women who were multiparous� Ž .�OR: 1.15, 95% C.I.: 1.06�1.24 , over 35 years

� Ž .� Ž .old 2.34 2.13�2.56 , and obese weight �91 kg� Ž .�2.36 2.00�2.80 , and women who had a prior

� Ž .�history of neonatal death 2.09 1.50�2.92 , his-� Ž .�tory of prior preterm delivery 1.25 1.03�1.51 ,

� Ž .�prior cesarean section 1.55 1.39�1.72 , and his-�tory of prior major fetal anomaly 1.49

Ž .� � Ž .�1.02�2.20 . Teenage mothers 0.34 0.27�0.43� Ž .�and women who smoked 0.81 0.77�0.92 or

� Ž .�drank alcohol 0.37 0.20�0.67 were less likely tohave GDM. After adjustment for confounders,multivariate logistic analysis finally indicated that

�women who were over 35 years old aOR: 2.34Ž .� � Ž .�2.13�2.58 , and obese aOR: 2.40 2.06�2.98 ,and women who had a history of neonatal death� Ž .�aOR: 1.19 1.06�1.34 , and had prior cesarean

� Ž .�section aOR: 1.18 1.11�1.25 were at higher risk�of having GDM. However, teenage mothers aOR:

Ž .�0.35 0.27�0.44 and women who drank alcohol� Ž .�aOR: 0.40 0.25�0.76 were less likely to haveGDM.

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Table 2Pregnancy outcomes of GDM, Alberta, Canada, 1991�1997

Outcomes Non-diabetes GDMŽ . Ž .N�108 664 N�2755

�Ž .Gestational age weeks 38.9 38.5��Ž .Birth weight g 3374.8 3460.2

��Apgar 1 7.58 7.44�Apgar 5 8.84 8.79

Apgar 10 9.11 9.11� �� Ž .P�0.05; P�0.01 analysis of variance .

Table 2 shows the impact of GDM on gestatio-nal age, birth weight, and Apgar scores. Themean gestational age was shorter in women withGDM than in women without GDM. The meanbirth weight was higher in women with GDMthan in women without GDM. The Apgar scoresat 1 and 5 min ware significantly lower in womenwith GDM than in women without GDM. How-ever, there was no difference in Apgar scores at10 min between the two groups of women.

Table 3 shows the effect of GDM on selectedmaternal and infant outcomes. Univariate analy-sis suggested that mothers with GDM were atmarkedly increased risk of having gestational hy-

� Ž .� �pertension 2.52 2.24�2.85 , pre-eclampsia 2.58Ž .�2.04�3.28 , premature rupture of membranes� Ž .� �1.41 1.17�1.69 , cesarean section 1.72Ž .� � Ž .�1.57�1.88 , and preterm birth 1.42 1.26�1.61 .Infants born to mothers with GDM were at higher

Ž .risk of being macrosomic birth weight �4200 g� Ž .�1.63 1.43�1.86 and large-for-gestational-age� Ž .�3.64 3.20�4.13 . However, infants born to moth-ers with GDM were not at higher risk of being

� Ž .�stillborn 0.83 0.41�1.67 . After adjusting forpotential confounding variables as listed in Table1, mothers with GDM were at significantly in-

�creased risk of gestational hypertension aOR:Ž .� �1.26 1.21�1.32 , pre-eclampsia aOR: 1.30

Ž .�1.20�1.41 , premature rupture of membranes� Ž .� �aOR: 1.13 1.06�1.20 , cesarean section aOR:

Ž .� �1.13 1.10�1.17 , and preterm delivery aOR: 1.13Ž .�1.08�1.18 . Infants born to mothers with GDM

�were at higher risk of macrosomia aOR: 1.12Ž .�1.07�1.17 or being large-for-gestational-age� Ž .�aOR: 1.43 1.37�1.50 .

4. Discussion

The reported prevalence of GDM variesbetween �1% and �10% depending on thedifferences in screening approaches, diagnostic

� �criteria and study populations 12,13 . There arealso great geographic and ethnic variations in the

� �prevalence of GDM 12,14 . Indeed, few previousstudies reporting the prevalence of GDM arepopulation-based. Most of reports originate fromeither tertiary care centers or obstetric clinics towhere women with GDM are likely to be re-ferred. The prevalence of GDM is therefore oftenoverstated. Our data include information from 39hospitals in northern and central Alberta. Thedata captured from 78 to 90% of deliveries foryears 1991 to 1994, and greater than 90% for theyear 1995, 95% for 1996, and 97% for 1997. Theprevalence of GDM ranges between 2.2 and 2.8%from 1991 to 1997, with an average rate of 2.5%.There is no trend toward increasing or decreasingrates over this period.

Our study confirms the previous reports thatthe risk factors for GDM are advancing ageŽ .especially, �35 years old , obesity, and a historyof neonatal death or a history of prior cesarean

� �section 4,13�15 . After adjustment for confoun-ders, our study does not show that other traditio-nal risk factors including multiparity, maternalsmoking, leaner stature, history of premature de-livery and major fetal anomaly are associated with

� �GDM 14,16 . Our finding of the protective effect�of maternal alcohol use against GDM aOR: 0.40

Ž . �0.25�0.76 , P � 0.01 is in agreement with� �McMahon et al.’s report 17 , which also shows

that GDM is also less likely to occur in women� Ž .who drank alcohol aOR: 0.78 0.61�0.98 , P�

�0.05 . However, it is not known whether this is adirect effect of maternal alcohol use per se ormediated by other covariates. Further studies ofthis association are warranted.

Our study supports previous reports that womenwith GDM have a higher proportion of obstetriccomplications including pregnancy-induced hy-

Žpertension gestational hypertension and pre-.eclampsia , premature membrane rupture, ce-

sarean section and preterm delivery, as well asfetuses that are of higher birth weight, are macro-

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Table 3Pregnancy outcomes of GDM, Alberta, Canada, 1991�1997

Outcomes Subjects Non-diabetes GDM Unadjusted OR Adjusted ORaŽ . Ž . Ž . Ž .N N�108 664 N�2755 95% C.I. 95% C.I.

Ž . Ž . Ž .% % %

Gestationalhypertension

Ž .No 105 855 95.0 95.2 88.6 � ��� ��Ž . Ž . Ž .Yes 5564 5.0 4.8 11.4 2.52 2.24�2.85 1.26 1.21�1.32

Pre-eclampsiaŽ .No 110 197 98.9 98.9 97.3 � �

�� ��Ž . Ž . Ž .Yes 1222 1.1 1.1 2.7 2.58 2.04�3.28 1.30 1.20�1.41Chronic

hypertensionŽ .No 110 600 99.3 99.3 99.0 � �Ž . Ž . Ž .Yes 819 0.7 0.7 1.0 1.40 0.96�2.05 0.99 0.87�1.13

Membranes ruptured�37 weeks

Ž .No 107 706 96.7 96.7 95.4 � ��� ��Ž . Ž . Ž .Yes 3710 3.3 3.3 4.6 1.41 1.17�1.69 1.13 1.06�1.20

Cesarean sectionŽ .No 93 138 83.6 83.8 75.1 �

�� ��Ž . Ž . Ž .Yes 18 281 16.4 16.2 24.9 1.72 1.57�1.88 1.13 1.10�1.17Preterm birthŽ .�37 weeks

Ž .No 102 960 92.4 92.5 89.6 � ��� ��Ž . Ž . Ž .Yes 8459 7.6 7.5 10.4 1.42 1.26�1.61 1.13 1.08�1.18

Low birth weightŽ .�2500 g

Ž .No 105 154 94.4 94.4 95.4 � ��Ž . Ž . Ž .Yes 6265 5.6 5.6 4.6 0.81 0.68�0.97 0.94 0.89�1.00

MacrosomiaŽ .�4200 g

Ž .No 104 707 94.0 94.1 90.7 � �� ��Ž . Ž . Ž .Yes 6712 6.0 5.9 9.3 1.63 1.43�1.86 1.12 1.07�1.17

SGAŽ .No 107 491 96.5 96.5 96.7 � �Ž . Ž . Ž .Yes 3927 3.5 3.5 3.3 0.94 0.77�1.17 1.00 0.94�1.08

LGAŽ .No 107 809 96.8 96.9 89.7 � �

�� ��Ž . Ž . Ž .Yes 3610 3.2 3.1 10.3 3.64 3.20�4.13 1.43 1.37�1.50Still birth

Ž .No 111 031 99.7 99.7 99.7 � �Ž . Ž . Ž .Yes 388 0.3 0.3 0.3 0.83 0.41�1.67 0.92 0.73�1.17

OR, odds ratio; 95% C.I., 95% confidence interval; � P�0.05; �� P�0.01.a By controlling for all variables in Table 1.

somic, and infants who are large-for-gestational-� �age 4,13,14,16 . Our study is in agreement with

Casey et al.’s report that GDM is not associated� �with an increased risk of stillbirth 16 .

The principal pregnancy complication at-tributable to GDM is excessive fetal size or

� �macrosomia 1,5 . Fetal macrosomia is the conse-quence of fetal hyperinsulinemia which resultsfrom increased maternal�fetal transfer of glucose

� �and other nutrients 18 . Fetal macrosomia couldcause difficulty during delivery as demonstrated

� �by complications such as shoulder dystocia 5 ,

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birth trauma and need of early or preterm deliv-� �ery or operative delivery 2�5 .

When comparing the GDM with the non-GDMgroup, the actual birth weight difference was only85 g, the gestational age difference was only 0.4weeks and the Apgar scores at 1 min differed by avalue of 0.14 and at 5 min by a value of 0.05Ž .Table 2 . These differences are statistically sig-nificant but are not clinically relevant. By adjust-ing for confounders such as maternal weight andage, the effects of GDM on pregnancy-inducedhypertension and LGA changes dramatically. TheLGA ORs change from a crude estimate of 3.64

Ž .to the adjusted one of 1.43 Table 3 . This sug-gests that the confounders of maternal advancingage and obesity themselves account for a signifi-cantly increased risk of pregnancy-induced hyper-tension and LGA babies. In fact, after adjustmentfor confounders, the impact of GDM per se onthe maternal and infant outcomes is reduced, allwith marginal aORs ranging from approximately1.12 to 1.49. However, it should be noted that theobserved impacts of GDM on maternal and in-fant outcomes occur under the current universalscreening, management and treatment of GDM.In addition, our data do not discriminate theeffect of diabetic diet or insulin therapy. There-fore, it is not known whether or not the therapyalters the effects of GDM on maternal and infantoutcomes. It is left to be debated if the effects ofGDM per se justify the universal screening, ther-apy, and fetal and maternal monitoring. Futurestudies are needed to compare the incidence ofGDM-related maternal and fetal morbidity suchas pre-eclampsia, premature rupture of mem-branes, cesarean section, preterm delivery,macrosomia and large-for-gestational before andafter installation of the universal screening forGDM and to examine whether there is a trend indecreasing GDM related maternal and fetal mor-bidity after universal screening of GDM. Largerandomized controlled trials of comparing univer-sal screening and selective screening of high riskpopulations will provide a final answer as towhether universal screening of GDM has anybenefit in decreasing maternal and fetal morbid-

� �ity 2 .

Acknowledgements

Dr Xu Xiong was supported by the CanadianInstitute of Health Research.

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