Prepregnancy Body Mass Index and Congenital Heart Defects among Offspring: A Population-based Study

Objective: The purpose of this study was to evaluate the association between fetal development of congenital heart defects (CHD) and maternal prepregnancy body mass index (BMI, kg/m²) in the largest population-based case-control study to date. Background: Mounting evidence implicates maternal obesity as a risk factor for birth defects. However, the association between maternal obesity and CHD in offspring has been less completely described. Methods: We conducted a study of CHD using linked birth-hospital discharge records for Washington State between 1992-2007. All infants with CHD (n = 14142) were identified based on ICD9-CM discharge diagnosis codes. 141420 controls, frequency matched on year of delivery, were selected at random from among infants without CHD. Maternal BMI was calculated from maternal prepregnancy data. Odds ratios (OR) and 95% confidence intervals (CI) for the association of CHD relative to maternal BMI were calculated, adjusted for gestational diabetes. Results: Infants with CHD were more likely to have an obese mother (OR 1.22, 95% CI 1.15-1.30). The strength of association increased with increasing BMI (BMI 30-34.9: OR 1.16, 95% CI 1.07-1.25; BMI 35-39.9: OR 1.25, 95% CI 1.13-1.39; BMI > = 40: OR 1.49, 95% CI 1.32-1.69). The association was greatest for left and right ventricular outflow tract defects (OR 1.27, 95% CI 1.02-1.59 and OR 1.43, 95% CI 1.20-1.69, respectively). Hypoplastic left heart syndrome was markedly associated (OR 1.86, 95% CI 1.13-3.05). There was no association with conotruncal defects (OR 1.04, 95% CI: 0.82-1.33). Conclusions: We confirmed the association between CHD and maternal obesity and observed increasing risk with increasing obesity. Outflow tract defects appear uniquely associated. A greater risk of CHD among offspring is an important outcome of maternal obesity, and suggests a need for targeted medical management strategies.