This study was done to determine if impaired glucose tolerance in pregnancy was associated with increased maternal and neonatal morbidity and if so, whether the increased morbidity was due to the confounding factors of increased maternal age and maternal obesity. It was a retrospective analysis to compare 944 women with impaired glucose tolerance (IGT) in pregnancy with 10,065 women without abnormal glucose tolerance. The incidence of impaired glucose tolerance in pregnancy was 8.6% in this study. Even when maternal age and obesity were excluded, the IGT group had significantly higher risks of labour induction (relative risk, RR, 1.15); Caesarean section (RR: overall 1.43, elective 1.72, emergency 1.31); Caesarean section for dystocia/no progress (RR 1.60); macrosomia (RR 1.69, 1.76, 1.61 for birth-weight > = 97th, 95th, 90th percentiles respectively) and shoulder dystocia (RR 2.84) when compared to the nondiabetics (NDM). The risks of hypertensive disease (RR 1.22) and Caesarean section for fetal distress/thick meconium-stained liquor (RR 1.53) were also higher in the IGT group but these increases were not statistically significant when maternal age and obesity were excluded. There was no significant difference in the rates of low Apgar scores at 1 and 5 minutes between the 2 groups.