Proportion of critical congenital heart defects attributable to unhealthy prepregnancy body mass index among women with live births in Florida, 2005-2016.

Background: Associations between maternal prepregnancy body mass index (BMI) and congenital heart defects have been reported, however, the proportion of critical congenital heart defects (CCHDs) attributable to unhealthy prepregnancy BMI has not been determined. Our objective was to investigate the association between maternal prepregnancy BMI and CCHDs.

Methods: The Florida Birth Defects Registry was used to identify infants with CCHDs born between 2005-2016. Birth certificate data were used to define the source population and identify perinatal and socio-demographic characteristics. BMI values were categorized as underweight (<18.5), normal weight (18.5-24.9), overweight (25.0-29.9), obese I (30.0-34.9), obese II (35.0-39.9), and obese III (≥40.0). Multi-predictor logistic regression models were used to estimate adjusted odds ratios (aORs) and 99% confidence intervals representing the association between maternal prepregnancy BMI and CCHDs. Adjusted population attributable fractions (PAFs) for the aORs were calculated.

Results: We observed a significantly increased risk of "any CCHD" in infants born to women at any level of obesity. Among the 12 CCHDs examined, 5 showed a significantly increased risk among mothers in the two highest obesity levels (II & III). Approximately 8% of all CCHDs may be attributed to suboptimal maternal prepregnancy BMI, with the highest total individual CCHD PAFs for pulmonary valve atresia (21.7%) and total anomalous pulmonary venous return (12.8%).

Conclusions: Women with suboptimal prepregnancy BMI are at increased odds of having a child born with a CCHD. We found evidence of a direct dose-response relationship between prepregnancy BMI and odds for CCHD; with variation by CCHD subtype.