IS MATERNAL OBESITY A RISK FACTOR FOR ANENCEPHALY AND SPINA-BIFIDA

To determine whether the risk of having an infant with anencephaly or spina bifida is greater among obese women than among average-weight wo men, we compared 307 Atlanta area women who gave birth to a liveborn o r stillborn infant with anencephaly or spina bifida (case group) with 2,755 Atlanta-area women who gave birth to an infant without birth def ects (control group). The infants of control women were randomly selec ted from birth certificates and frequency-matched to the case group by race, birth hospital, and birth period from 1968 through 1980. After adjusting for maternal age, education, smoking status, alcohol use, ch ronic illness, and vitamin use, we found that, compared with average-w eight women, obese women (pregravid body mass index greater than 29) h ad almost twice the risk of having an infant with spina bifida or anen cephaly (odds ratio=1.9; 95% confidence limits=1.1, 3.4). A woman's ri sk increased with her body mass index: adjusted odds ratios ranged fro m 0.6 (95% confidence limits=0.3, 2.1) for very underweight women to 1 .9 for obese women.