This prospective observational study was done to analyse the prevalence of gestational diabetes mellitus (GDM) among primigravidae and its outcome. All healthy primigravidae with singleton pregnancies were offered universal glucose tolerance testing between 16 and 28 weeks gestation. GDM and non GDM groups were managed according to hospital protocol. The antenatal features and pregnancy outcomes were analysed. Out of 616 primigravidae, 113 (18.34%) were GDM with slightly older (27.9 +/- 4.2 versus 26.32 +/- 3.3, p < 0.001) age. The mean fasting and two hours postprandial blood glucose in both groups were 4.99 +/- 1.08 mmol/l, 8.86 +/- 1.41 mmol/l(GDM) and 4.36 +/- 0.43 mmol/l, 5.71 +/- 1.11 mmol/l (Non GDM), respectively. Maternal family history of diabetes mellitus, weight exceeding 80 Kg, polyhydramnios (2.65% versus 0.2%, p = 0.028) and neonatal hyperbilirubinaemia (9.73% versus 2.98%, p = 0.01) occurred significantly more frequent in the GDM group compared to normal. There was no significant difference in other pregnancy outcomes and complications between the two groups. In conclusion GDM in primigravidae was detected at a relatively young age with more frequent maternal family history of DM, weight exceeding 80 Kg, polyhydromnions and neonatal hyperbilirubinaemia. The degree of disease was mild and treatment led to no significant complication.