Maternal occupational exposure to organic solvents during early pregnancy and risks of neural tube defects and orofacial clefts

Objectives Though toxicological experiments demonstrate the teratogenicity of organic solvents in animal models, epidemiologic studies have reported inconsistent results. Using data from the population-based National Birth Defects Prevention Study, the authors examined the relation between maternal occupational exposure to aromatic solvents, chlorinated solvents and Stoddard solvent during early pregnancy and neural tube defects (NTDs) and orofacial clefts (OFCs). Methods Cases of NTDs (anencephaly, spina bifida and encephalocoele) and OFCs (cleft lip +/- cleft palate and cleft palate alone) delivered between 1997 and 2002 were identified by birth defect surveillance registries in eight states; non-malformed control infants were selected using birth certificates or hospital records. Maternal solvent exposure was estimated by industrial hygienist review of self-reported occupational histories in combination with a literature-derived exposure database. ORs and 95% CIs for the association between solvent class and each birth defect group and component phenotype were estimated using multivariable logistic regression, adjusting for maternal age, race/ethnicity, education, pre-pregnancy body mass index, folic acid supplement use and smoking. Results The prevalence of exposure to any solvent among mothers of NTD cases (n=511), OFC cases (n=1163) and controls (n=2977) was 13.1%, 9.6% and 8.2%, respectively. Exposure to chlorinated solvents was associated with increased odds of NTDs (OR=1.96, CI 1.34 to 2.87), especially spina bifida (OR=2.26, CI 1.44 to 3.53). No solvent class was strongly associated with OFCs in these data. Conclusions The findings suggest that maternal occupational exposure to chlorinated solvents during early pregnancy is positively associated with the prevalence of NTDs in offspring.