Some studies showed incidence of GDM in pregnant women with PCO was higher than normal group (19). Similarly in our study the risk of GDM was 1.54 in women with PCO. However, we defined PCO according to history of irregular menstruation and/or hirsutism before pregnancy and it was not an accurate diagnostic tool for PCO (20). We did not have ultrasound finding about PCO before pregnancy. In our study there was no significant association between height and GDM. Unlike the other studies which reported that GDM tends to occur more frequently in women who are short (21-23). After logistic regression analysis, GDM was significantly correlated with age, pre pregnancy BMI, family history of diabetes, history of PCO, history of GDM and previous adverse outcome of pregnancy. These results are in concordance with other studies (15-18).