The aim of the present study was to examine the associations of gestational diabetes mellitus (GDM) and impaired glucose tolerance (IGT) with maternal and fetal outcomes.A total of 200 pregnant women were included in this cross-sectional study. A 50-gram oral glucose challenge test (GCT) was performed between 24 and 28 weeks of gestation, followed by glucose tolerance test (OGTT) with 100 grams of oral glucose in those with an abnormal one-hour test result. The following were not significantly different between groups. Preterm labour (PL), pregnancy induced hypertension(PIH), pre-eclampsia, polyhydramnios, and macrosomia. However, a significant increase was noted in the fetal birth weight as well as in number of cesarean deliveries among GDM subjects. Neonatal outcomes were also similar between the two groups. In conclusion, the present results suggest that single high glucose readings in OGTT may be as important as a diagnosis of GDM in terms of fetomaternal complication risk.