Maternal occupational exposure to polycyclic aromatic hydrocarbons and risk of neural tube defect-affected pregnancies.

Background: This study evaluated whether there is an association between maternal occupational exposure to polycyclic aromatic hydrocarbons (PAHs) and neural tube defects (NTDs) in offspring. This is the first such study of which the authors are aware.

Methods: Data were analyzed from 1997 to 2002 deliveries in the National Birth Defects Prevention Study, a large population-based case-control study in the United States. Maternal interviews yielded information on jobs held in the month before through 3 months after conception. Three industrial hygienists blinded to case or control status assessed occupational exposure to PAHs. Crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were estimated using unconditional logistic regression.

Results: Of the 520 mothers of children with NTDs, 5.0% were classified as exposed to occupational PAHs, as were 3.5% of the 2989 mothers of controls. The crude OR for PAH exposure was 1.43 (95% CI, 0.92-2.22) for any NTD and 1.71 (95% CI, 1.03-2.83) for spina bifida. Adjusted ORs were smaller in magnitude and not significant. Among women who were normal weight or underweight, the crude OR for spina bifida was 3.13 (95% CI, 1.63-6.03) and adjusted OR was 2.59 (95% CI, 1.32-5.07). Based on estimated cumulative exposure, a statistically significant dose-response trend was observed for spina bifida; however, it was attenuated and no longer significant after adjustment.

Conclusion: Maternal occupational exposure to PAHs may be associated with increased risk of spina bifida in offspring among women who are normal weight or underweight. Other comparisons between PAHs and NTDs were consistent with no association.