Nonsyndromic orofacial clefts are common birth defects. Reported risks for orofacial clefts associated with parental occupational pesticide exposure are mixed. To examine the role of parental pesticide exposure in orofacial cleft development in offspring, this study compared population-based case-control data for parental occupational exposures to insecticides, herbicides, and fungicides, alone or in combinations, during maternal (1 month before through 3 months after conception) and paternal (3 months before through 3 months after conception) critical exposure periods between orofacial cleft cases and unaffected controls. Multivariable logistic regression was used to estimate odds ratios, adjusted for relevant covariables, and 95% confidence intervals for any (yes, no) and cumulative (none, low [<median exposure level in controls], high [≥median exposure level in controls]) occupational pesticide exposures and cleft lip ± cleft palate and cleft palate. Associations for cleft lip ± cleft palate tended to be near unity for maternal or paternal occupational pesticide exposures, except for low paternal exposure to any pesticide, which produced a statistically significant inverse association with this subtype. Associations for cleft palate tended to be near unity for maternal exposures and mostly positive, but non-significant, for paternal exposures; a significant positive association was observed between paternal low exposure to insecticide + herbicide + fungicide and cleft palate. Combined parental exposure produced non-significant associations near or below unity for all orofacial cleft cases combined and cleft lip ± cleft palate and positive, but non-significant, associations for cleft palate. This study observed associations mostly near unity between maternal occupational pesticide exposure and orofacial clefts. Associations for paternal occupational pesticide exposures were mostly near or below unity for cleft lip ± cleft palate, and mostly positive for cleft palate. However, due to the limitations of this study, these subtype-specific results should be interpreted cautiously. Future research examining parental occupational pesticide exposure and orofacial clefts should attempt to improve exposure assessment and increase sample size to better facilitate risk estimation.
Keywords: Cleft lip; cleft palate; herbicides; insecticides; pesticides; pregnancy.