Overweight or obese: The impact of Body Mass Index (BMI) on rates of gestational diabetes

Abstract

BACKGROUND: The prevalence of maternal obesity is on the rise. A number of adverse pregnancy outcomes are associated with increasing maternal BMI; these include hypertension, cesarean delivery, and gestational diabetes. OBJECTIVE: Our objective was to compare rates of gestational diabetes (GDM) in normal to underweight, overweight, and obese gravidas, further subdividing the obese group into three classes. STUDY DESIGN: We reviewed data from the Consortium for Safe Labor. Records from 9227 deliveries, between 2004 and 2007, at four Medstar Health hospitals were reviewed; using prepregnancy BMI, we compared normal weight gravitas (BMI 18.50-24.99kg/m2) to underweight gravidas (BMI <18.50kg/ m2), overweight gravidas (BMI between 25-29.99kg/m2), obese I gravidas (BMI 30-34.99kg/m2), obese II gravidas (35-39.99kg/m2), and obese III gravidas (BMI >40kg/m2) and recorded their rates of gestational diabetes. The rates of gestational diabetes were compared using the Chi-Square statistic or Fisher's Exact Test (SAS version 9.1.3). Statistical significance was set at p<0.05. RESULTS: The risk of GDM increases progressively with every category of BMI. The odds ratio for the development of gestational diabetes as compared to normal weight gravidas was 2.14, 3.67, 4.82, and 5.90 for overweight, obese I, obese II, and obese III, respectively. While being underweight appeared protective against the development of gestational diabetes (OR=0.41), this result is limited by the small number of cases in this group. (Table presented) CONCLUSION: The risk of developing GDM is positively correlated with BMI over the entire range of BMI, even demonstrating progressive increase within the obese range. Therefore, even modest reductions in BMI may reduce the risk of developing GDM by as much as two-fold, regardless of the severity of obesity.