A cohort study on 1071 Iranian pregnant women was performed from 2007 to 2009. This study was approved by the Shahid Sadoughi University of Medical Science Ethical Committees. The participants were recruited from two prenatal clinics in Yazd, after obtaining informed consent for the scientific use of the data. Women with diabetes before pregnancy were not included in the study. From their medical records, information was obtained including maternal age, parity, gestational age, height, pre-pregnancy weight, systolic and diastolic blood pressure at the first prenatal visit, and reproductive and medical histories which were entered in analysis of the data as covariates.