GDM has been recognized for decades, but controversies remain regarding the screening test and diagnostic criteria. There is general consensus that incidence of GDM is increasing globally. The incidence of GDM in the current study was 10.2% within the reported range in literature (6), but was higher than in other studies in Iran (7). This difference may be related to the screening methods, diagnostic criteria used or population studied. Another reason for this difference might be high prevalence of type 2 diabetes in Yazd (8).