Zahra Shahshahan1, Bahram Heshmati2, Mojtaba Akbari3, Fahimeh Sabet. 1. Department of Obstetrics and Gynecology, Shahid Beheshti Hospital, Isfahan University of Medical Sciences, Isfahan 81746-73461, Iran. Electronic address: fsabet@med.mui.ac.ir. 2. Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran. 3. Department of Epidemiology, School of Health and Nutrition, Shiraz University of Medical Science, Shiraz, Iran.