Maternal obesity and risk for birth defects.

OBJECTIVE Several studies have shown an increased risk for neural tube defects associated with prepregnancy maternal obesity. Because few recent studies have examined the relation between maternal prepregnancy obesity and overweight and other birth defects, we explored the relation for several birth defects and compared our findings with those of previous studies. METHODS We conducted a population-based case-control study of several selected major birth defects using data from the Atlanta Birth Defects Risk Factor Surveillance Study. Mothers who delivered an infant with and without selected birth defects in a 5-county metropolitan Atlanta area between January 1993 and August 1997 were interviewed. Maternal body mass index (BMI) was calculated from self-reported maternal prepregnancy weight and height. Women with known preexisting diabetes were excluded. The risks for obese women (BMI > or =30) and overweight women (BMI 25.0-29.9) were compared with those for average-weight women (BMI 18.5-24.9). RESULTS Obese women were more likely than average-weight women to have an infant with spina bifida (unadjusted odds ratio [OR]: 3.5; 95% confidence interval [CI]: 1.2-10.3), omphalocele (OR: 3.3; 95% CI: 1.0-10.3), heart defects (OR: 2.0; 95% CI: 1.2-3.4), and multiple anomalies (OR: 2.0; 95% CI: 1.0-3.8). Overweight women were more likely than average-weight women to have infants with heart defects (OR: 2.0; 95% CI: 1.2-3.1) and multiple anomalies (OR: 1.9; 95% CI: 1.1-3.4). CONCLUSIONS Our study confirmed the previously established association between spina bifida and prepregnancy maternal obesity and found an association for omphalocele, heart defects, and multiple anomalies among infants of obese women. We also found an association between heart defects and multiple anomalies and being overweight before pregnancy. A higher risk for some birth defects is yet another adverse pregnancy outcome associated with maternal obesity. Obesity prevention efforts are needed to increase the number of women who are of healthy weight before pregnancy.