An abnormal glucose tolerance which is first detected during pregnancy and disappears after completion of pregnancy is known as "gestational diabetes mellitus". Early detection of this condition helps preventing potential maternal and fetal complications. Some studies reported that platelets may have a role in the pathogenesis and development of gestational diabetes. In the present study, we aimed to evaluate and compare the platelet function and morphology among pregnant women with gestational diabetes and healthy pregnant women. Values of complete blood count were reviewed for pregnant women between weeks 24 and 28 of gestation while performing oral glucose tolerance tests for from January 2013 to September 2013. After screening, a total of 89 pregnant women were enrolled in the study including 38 women with gestational diabetes and 51 healthy pregnant women. The mean platelet volume (MPV) was 8.76 +/- 1.53 fl in the group with gestational diabetes and 7.80 +/- 1.34 fl in the healthy pregnant group, with a statistically significant difference between two groups (P=0.02). There was no statistically significant difference between two groups in platelet counts (P=0.25). Dissimilar results were reported by a small number of studies on this subject. MPV and other platelet parameters may be considerably helpful in detecting diabetic pregnant women who are at risk for vascular complications. In this study, significantly greater MPV was found among pregnant women with gestational diabetes compared to control group (P<0.05). Further studies are needed to elucidate the role of such changes and their potential clinical implications in women with gestational diabetes.