Seyed-Saeed Hashemi-Nazari - Ph.D in Epidemiology, Department of Epidemiology, Safety Promotion and Injury Prevention Research Center, School of public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Farid Najafi - Ph.D in Epidemiology, Department of Epidemiology, Research Center for Environmental Determinants of Health (RCEDH), Kermanshah University of Medical Sciences, Kermanshah, Iran
Mehr-Ali Rahimi - MD of Endocrinology, Diabetes Research Center, Department of Internal Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
Neda Izadi - Ph.D Student, Student Research Committee, Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Background: Gestational diabetes mellitus (GDM) is the most common medical problem during pregnancy. High and low maternal BMI plays a role in some of the complications of pregnancy. This study aims to investigate the GDM and the dose-response association of BMI with it in pregnant women in Kermanshah, Iran Methods: In this retrospective cohort study, the 1010 pregnant women referring to 10 health centers in Kermanshah city of Iran during the 2015-16 year were studied. Data collection formincluded age, parity, BMI at the beginning of pregnancy, family history of type 2 diabetes, history of GDM and abortion. The restricted cubic spline method was used to evaluate the relationship between BMI and GDM Results: The median age of pregnant women was 28 (IQR=8) years. The risk of GDM was 10.1% (102 subjects). Using multivariate model the risk of GDM among obese pregnant women were higher than those who were overweight. The inverse dose-response relationship wasassociated with a significant change the risk of GDM as per 1 kg/m2 increase in BMI. The incidence rate ratio for GDM indicates a non-significant protective effect and, then a significant risk for GDM occurrence along with BMI Conclusions: In the present study the inverse dose-response relationship between the level of BMI and the risk of GDM after adjusting for age, parity, family history of type 2 diabetes, history of GDM and abortion was seen. Such result shows that BMI can be used as a predictive factor. A healthy diet and recommended levels of physical activity are suggested to prevent overweight and obesity and subsequent GDM.

Gestational Diabetes Mellitus, Dose-Response, Body Mass Index, Pregnant Women