Objective: To evaluate the effect of pre-pregnancy body mass index (BMI) on the risk of developing gestational diabetes mellitus (GDM) in a large unselected population.
Methods: We performed a case control study using data collected in The Consortium on Safe Labor database. The association between BMI and GDM was evaluated both using BMI weight categories adopted by the National Institute of Health, and separately using BMI as a continuous variable. Multiple logistic regression analyses were used to evaluate the effects of BMI, age, ethnicity, parity, chronic hypertension and antenatal steroid use on the risk of GDM. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to approximate relative risks of GDM. A p value of <0.05 was considered significant.
Results: After controlling for other factors, the risk of GDM increased with an increasing BMI across all weight categories. For each 1 kg/m(2) increase of BMI the OR of developing GDM was 1.08 (95% CI 1.08-1.09) and for each 5 kg/m(2) increase, the OR was 1.48 (95% CI 1.45-1.51).
Conclusions: GDM is a multifactorial disorder and pre-pregnancy BMI plays an important role in that risk. Modest changes in pre-pregnancy BMI may decrease the risk of GDM substantially.