Background: Glucose metabolism impairment may occur during some pregnancies especially of advanced age and history of previous gestational diabetes and may result in hazardous consequences both for mother and neonate.

Methods: The present study as a case-control was conducted on 420 referred pregnant women to Shiraz hospitals that involve 70 diabetic patients and 350 non-diabetic women. Data analyzed by analysis of variance and χ square for univariate and logistic regression for multivariate analysis.

Results: From 70 diabetic patients 22(31.4%) afflicted with overt diabetes as well as 48 (68.6%) gestational diabetes. Gestational diabetes history (OR=23.14), hydramnious (OR=13.26), glucosuria at 3^rd trimester (OR=11.49), family history of diabetes (OR=4.09) and age (OR=1.03) were the most important risk factors for gestational diabetes, respectively. History of macrosomia in previous pregnancies (OR=18.83) and history of previous cesarean section (OR=11.96) were the most important predictors for overt diabetes.

Conclusion: In view of several threatening consequences of diabetes during pregnancy, screening for diabetes especially in mothers with gestational diabetes history and family history of diabetes is essential in order to control and prevention of these outcomes in mother and neonate.