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BACKGROUND: Maternal obesity, gestational diabetes (GDM), and gestational hypertension (GHTN) are associated with risks for adverse outcomes including cesarean delivery, macrosomia, low birth weight infants, and infant death. In the District of Columbia (DC), trends of increasing maternal obesity differ between racial/ethnic groups. This study investigated associations between maternal pre-pregnancy body mass index (BMI) and GDM and GHTN.
METHODS: We analyzed 18,264 live, singleton births in DC during 2009 to 2011. The study was restricted to birth records with maternal BMI data. Women who had diabetes or hypertension prior to pregnancy, unknown status of diabetes or hypertension, or had missing parity information were excluded. Maternal BMI was calculated from pre-pregnancy height and weight, categorized as underweight (<18.5 kg/m2), normal (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), and obesity (≥30 kg/m2). Using logistic regression models, odds ratios (OR) and 95% confidence intervals (CI) were calculated for associations of BMI with GDM and GHTN, adjusting for race/ethnicity, maternal age, and parity. Tests for interaction between BMI and race/ethnicity were performed using a likelihood ratio test. All analyses were performed using SAS v9.3.
RESULTS: This study population was 57% non-Hispanic Black, 29% non-Hispanic White, and 14% Hispanic. Overall, 20% of women were overweight and 23% were obese. The prevalence of GDM in non-Hispanic Black, non-Hispanic White, and Hispanic mothers was 2.8%, 2.1%, and 4.7%, respectively. Additionally, GHTN was prevalent in 4.5%, 2.3%, and 2.7%, respectively. There was no evidence of significant interactions between BMI and race/ethnicity associated with either GDM (p=0.36) or GHTN (p=0.64). Compared to normal, overweight and obesity were associated with increased risks of GDM (OR=1.90, 95%CI 1.51-2.39 and OR=2.86 95%CI 2.27-3.61, respectively) and GHTN (OR=1.68, 95%CI 1.36-2.07 and OR=2.83 95%CI 2.31-3.45, respectively). However, underweight was protective for both GDM and GHTN (OR=0.70 95%CI 0.36-1.38 and OR=0.66 95%CI 0.38-1.14).
CONCLUSIONS: Maternal BMI was positively associated with GDM and GHTN, without variations by race/ethnicity. Reducing maternal pre-pregnancy overweight and obesity could decrease risks for GDM and GHTN. These results may have implications for lowering other adverse pregnancy and birth outcomes associated with GDM and GHTN. Future studies are needed to determine whether undiagnosed diabetes and hypertension prior to pregnancy may contribute to the observed prevalence of GDM and GHTN.