Meta-analysis: Pesticides and orofacial clefts

Objective: The risk of orofacial clefts associated with pesticide exposure was examined by conducting a meta-analysis of studies published from 1966 through 2005. Design: The full text of 230 studies was reviewed in detail, and of these, 19 studies were included in the final analysis. Fixed effects and random effects models were used to calculate pooled odds ratios (ORs) and 95% confidence intervals (CIs), and homogeneity among studies was evaluated. Main outcome measures: Exposure- and phenotype-specific risks associated with pesticides. Results: Many of the studies identified as suitable for analysis used a retrospective design with varying sample sizes, levels of exposure assessment, and phenotype evaluation. For all phenotypes combined, maternal occupational exposure was associated with an increased risk of clefting (OR = 1.37; CI = 1.04 to 1.81), whereas the estimates were somewhat weaker for paternal occupational exposures (OR = 1.16; CI = 0.94 to 1.44) or for any residential exposure (OR = 0.77; CI = 0.20 to 2.96). Calculation of pooled estimates for individual cleft phenotypes was mostly limited to studies of paternal occupational exposure; estimates exceeded unity but were not statistically significant. Conclusions: The results of this meta-analysis suggest that maternal exposure to pesticides is associated with a modest but marginally significant risk of clefting. To better understand the relationship between pesticide exposure and orofacial clefts, future studies should consider evaluation of multiple routes of parental exposure, etiologically homogenous phenotypes, and individual genetic susceptibility.