Selected environmental exposures and risk of neural tube defects

Abstract

With a birth prevalence of 1 in 1000, neural tube defects (NTD)s contribute considerably to morbidity and healthcare costs. Known genetic and environmental (noninherited) risk factors for NTDs account for a small portion of risk, suggesting unidentified risk factors. In animal studies, maternal alcohol and pesticide exposures, independently, led to excess neural cell death, resulting in too few cells for neural tube closure. Human studies report no association between alcohol exposure and NTDs, but small to moderate positive associations for pesticide exposure. Such human etiologic studies of NTDs require a large base population, but frequently include only live births. Exclusion of cases by pregnancy outcomes may create ascertainment and response bias, complicating interpretation of findings. Using data from the National Birth Defects Prevention Study (NBDPS) and the Iowa Registry for Congenital and Inherited Disorders (IRCID), the independent effects of maternal periconceptional (1 month prior through 2 months postconception) alcohol and occupational pesticide exposure on the development of NTDs were examined, and differences in Iowa NTD cases were characterized by pregnancy outcome. Maternal reports of alcohol exposure were obtained for 1223 NTD case infants and 6807 control infants. Adjusted odds ratios, estimated using multivariate logistic regression, were near unity for NTDs by any maternal alcohol exposure, binge episode(s), and type(s) of alcohol consumed. Occupational pesticide exposure was assigned by industrial hygienists for mothers of 502 case and 2950 control infants. Adjusted odds ratios for any exposure and cumulative exposure to any pesticide,