normoglycemia is defined as a fasting blood glucose < 5.6 mmol / l and 2-h value < 7.8 mmol / l ( 5 ) . maternal bmi ( kg / m ) was calculated at the first obstetrical visit and defined as < 25 kg / m normal bmi ( nbmi ) , overweight ( ow ) 2529.9 kg / m , and obese ( ob ) 30 kg / m . maternal outcomes included caesarean deliveries , antepartum ( aph ) and postpartum ( pph ) hemorrhage , pregnancy - induced hypertension ( pih ) , and preeclampsia ( pet ) . fetal / infant outcomes included gestational weight at delivery , macrosomia , shoulder dystocia , major congenital malformations , miscarriage , stillbirth , neonatal death , and perinatal mortality . statistical analyses were carried out using the statistical package for the social sciences version 15.0 . a total of 2,329 women , mean  sd age 31.4  5.4 years , 90% caucasian with a recorded booking bmi and a normal ogtt , were included . caesarean deliveries increased from 16.4 to 23.4 to 32.6% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the odds ratio ( or ) of a caesarean delivery was 1.57 ( 95% ci 1.241.98 , p < 0.01 ) for ow and 2.65 ( 2.033.46 , p < 0.01 ) for ob women ( table 1 ) . the risk of an emergency caesarean delivery increased from 10 to 12.4 to 16.1% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the trend was similar for elective caesarean delivery , increasing from 6.5 to 11 to 16.5% nbmi , ow , and ob women , respectively ( p < 0.01 ) . ors and cis of caesarean section and hypertensive disorders of pregnancy * pregnancy - induced hypertension or preeclampsia . pih increased from 4.3 to 9 to 11.3% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . pet risk doubled from 2.7 to 4.7 to 6% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the overall risk of hypertensive disorders increased from 5 to 9.7 to 12.7% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the or of having a pregnancy complicated by hypertension was 2.30 ( 95% ci 1.553.40 , p < 0.01 ) in ow and 3.29 ( 2.145.05 , p < 0.01 ) in ob women ( table 1 ) . a total of 41.2% of ob women had a history of more than one miscarriage , compared with 34.7 and 32.5% in ow and nbmi women , repectively ( p < 0.01 ) . the or of a history of miscarriage was 1.4 ( 95% ci 1.111.77 in ob women , p < 0.01 ) . mean (  sd ) birth weight was 3.46  0.53 , 3.54  0.59 , and 3.62  0.55 kg in babies of nbmi , ow , and ob women , respectively ( p < 0.01 ) . the percentage of macrosomic babies ( > 4 kg ) increased from 15.5 to 21.4 to 27.8% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . a total of 4.1% of babies ( > 4 kg ) compared with 0.2% of babies ( < 4 kg ) had shoulder dystocia ( p < 0.01 ) . the or of a malformation was 2.47 ( 1.095.60 , p = 0.03 ) in ob women . fourteen ( 0.6% ) stillbirths and two ( 0.1% ) neonatal deaths occurred with a pmr of 6 of 1,000 . a total of 2,329 women , mean  sd age 31.4  5.4 years , 90% caucasian with a recorded booking bmi and a normal ogtt , were included . caesarean deliveries increased from 16.4 to 23.4 to 32.6% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the odds ratio ( or ) of a caesarean delivery was 1.57 ( 95% ci 1.241.98 , p < 0.01 ) for ow and 2.65 ( 2.033.46 , p < 0.01 ) for ob women ( table 1 ) . the risk of an emergency caesarean delivery increased from 10 to 12.4 to 16.1% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the trend was similar for elective caesarean delivery , increasing from 6.5 to 11 to 16.5% nbmi , ow , and ob women , respectively ( p < 0.01 ) . ors and cis of caesarean section and hypertensive disorders of pregnancy * pregnancy - induced hypertension or preeclampsia . pih increased from 4.3 to 9 to 11.3% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . pet risk doubled from 2.7 to 4.7 to 6% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the overall risk of hypertensive disorders increased from 5 to 9.7 to 12.7% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . the or of having a pregnancy complicated by hypertension was 2.30 ( 95% ci 1.553.40 , p < 0.01 ) in ow and 3.29 ( 2.145.05 , p < 0.01 ) in ob women ( table 1 ) . a total of 41.2% of ob women had a history of more than one miscarriage , compared with 34.7 and 32.5% in ow and nbmi women , repectively ( p < 0.01 ) . the or of a history of miscarriage was 1.4 ( 95% ci 1.111.77 in ob women , p < 0.01 ) . mean (  sd ) birth weight was 3.46  0.53 , 3.54  0.59 , and 3.62  0.55 kg in babies of nbmi , ow , and ob women , respectively ( p < 0.01 ) . the percentage of macrosomic babies ( > 4 kg ) increased from 15.5 to 21.4 to 27.8% in nbmi , ow , and ob women , respectively ( p < 0.01 ) . a total of 4.1% of babies ( > 4 kg ) compared with 0.2% of babies ( < 4 kg ) had shoulder dystocia ( p < 0.01 ) . the or of a malformation was 2.47 ( 1.095.60 , p = 0.03 ) in ob women . fourteen ( 0.6% ) stillbirths and two ( 0.1% ) neonatal deaths occurred with a pmr of 6 of 1,000 . obesity is a risk factor for adverse pregnancy outcome , but the potential contribution from undiagnosed hyperglycemia is not always excluded ( 68 ) . we excluded diabetes and demonstrated increased adverse events with increased bmi . rates of emergency caesarean delivery / elective caesarean delivery increased in ow and ob women . the higher rates of emergency caesarean delivery are likely to be more than a reflection of local obstetric practice , as 14.2% infants delivered by emergency caesarean delivery versus 6% by elective caesarean delivery and 3.6% vaginally were admitted to the neonatal intensive care unit ( p < 0.01 ) . an overview of 13 studies involving a million women suggests that the risk of pet doubles with every 57 kg / m increase in bmi ( 9 ) . our findings were broadly similar with an approximate doubling of risk of pih in the presence of obesity . this is a significant finding given that hypertensive disorders are the third leading cause of maternal death ( 10 ) , with a suggestion that long - term cardiovascular mortality may be increased ( 6 ) . in addition to birth injury , macrosomia is linked to increased obesity and dysglycemia in adolescence ( 12 ) . we found a strong association between obesity , macrosomia , and shoulder dystocia . a meta - analysis by stothard et al . the authors recognized in their conclusion that some of these adverse outcomes may be due to undiagnosed hyperglycemia . we found a significantly higher rate of congenital malformations in ob women ( or 2.47 ) but had excluded diabetes . previous studies have tried to disentangle the effects of obesity and diabetes on pregnancy outcome . jensen et al . ( 2 ) found an increased risk of adverse events in ow / ob glucose - tolerant danish women . these women were selected on the basis of increased risk of gdm , thereby limiting the application of the findings to the general population . our study was in an unselected population offered universal screening for gdm , and the results are therefore more applicable to the general obstetric population . in an earlier study , jensen demonstrated increasing risk of shoulder dystocia and macrosomia with increasing increments in fasting and 2-h glucose values , but patients with impaired glucose tolerance were not excluded ( 3 ) . we recognize that despite excluding women with gdm / impaired glucose tolerance , there is evidence that even lesser degrees of hyperglycemia may still carry additional risk of adverse outcomes , as demonstrated in the hyperglycemia and adverse pregnancy outcome ( hapo ) study ( 14 ) . obesity confers an increased lifetime risk for type 2 diabetes , and research has offered potential interventions to retard this ( 15 ) . obese women could be offered prepregnancy care with a focus on promoting nbmi prior to their next pregnancy . further studies are needed to compare outcomes of obese women who undergo intensive prepregnancy care compared with those with no intervention .
objectivea prospective study of the impact of obesity on pregnancy outcome in glucose - tolerant women.research design and methodsthe irish atlantic diabetes in pregnancy network advocates universal screening for gestational diabetes . 
 women with normoglycemia and a recorded booking bmi were included . 
 maternal and infant outcomes correlated with booking bmi are reported.resultsa total of 2,329 women fulfilled the criteria . 
 caesarean deliveries increased in overweight ( ow ) ( odds ratio 1.57 [ 95% ci 1.241.98 ] ) and obese ( ob ) ( 2.65 [ 2.033.46 ] ) women . hypertensive disorders increased in ow ( 2.30 [ 1.553.40 ] ) and ob ( 3.29 [ 2.145.05 ] ) women . reported miscarriages increased in ob ( 1.4 [ 1.111.77 ] ) women 
 . 
 mean birth weight was 3.46 kg in normal bmi ( nbmi ) , 3.54 kg in ow , and 3.62 kg in ob ( p < 0.01 ) mothers . 
 macrosomia occurred in 15.5 , 21.4 , and 27.8% of babies of nbmi , ow , and ob mothers , respectively ( p < 0.01 ) . 
 shoulder dystocia occur in 4% ( > 4 kg ) compared with 0.2% ( < 4 kg ) babies ( p < 0.01 ) . 
 congenital malformation risk increased for ob ( 2.47 [ 1.095.60 ] ) women.conclusionsow and ob glucose - tolerant women have greater adverse pregnancy outcomes .