Relationship between body mass index and gestational diabetes mellitus

Background: Gestational diabetes mellitus (GDM) is one of the most common medical complications in pregnancy, which is associated with many serious consequences for mother and her fetus. Body mass index (BMI) in pregnant women is considered as one of most effective factor for the incidence of GDM. The aim of this study was to determine the relationship between BMI at pregnant women in the early months of pregnancy and the incidence of GDM. Methods: In this retrospective cohort study, the case of six hundred fifty-nine pregnant women who referred to health centers in Kermanshah City from September 2010 to September 2012 by convenience sampling method were selected and investigated. This study was sponsored by Kermanshah University of Medical Sciences. Height and weight were measured for each woman at the beginning of pregnancy and maternal body mass index (BMI) was calculated based on height and weight measurements. Then the pregnant women were divided into four groups based on BMI: thin (BMI less than 18.9 kg/m2), normal (BMI between 19 kg/m2 and 24.9 kg/m2), overweight (BMI between 25 kg/m2 and 29.9 kg/m2) and obese (BMI more than 30 kg/m2). Those women who had diabetes at the beginning of pregnancy were excluded from the study. GDM was considered as fasting blood glucose ≥92 between 26-30 weeks of gestation. Results: The mean±SD age of pregnant women was 27.7±5.85 year and the mean of BMI was 24.4±4.0 kg/m2. The GDM was shown in 30.7% of women. Association between BMI and GDM were statistically significant (P<0.001). The risk of GDM onset was 1.24 times, for each unit increased in BMI, (P<0.001). The risk of GDM was significantly higher in overweight [OR=2.97, CI (2.01-4.39)] and obese [OR=16.89, CI (8.46-33.70)] women. Being underweight increased the risk of GDM onset up to 1.19 times, but not significant. Conclusion: There is a significant relationship between maternal BMI in pregnant women at the beginning of pregnancy with GDM onset. Increased BMI is correlated with an increase in the incidence of GDM.