Maternal exposure to ambient air pollutant and risk of oral clefts in Wuhan, China

Maternal exposure to ambient air pollution has been related to oral clefts in offspring; however, the epidemiologic evidence is equivocal. Especially, the association between high levels of exposure to ambient air pollution during pregnancy and oral clefts remains unclear. The objective of this study was to evaluate whether high levels of maternal exposure to PM2.5, PM10, O3, CO and SO2 are related to increased risk of oral clefts in Wuhan, China. A population-based study was conducted using cohort of 105,927 live-born infants, fetal deaths, and stillbirths during a two-year period from 2011 to 2013. For each participant, weekly and monthly averages of daily mean concentrations for each pollutant were estimated. Multiple logistic regression analyses were constructed to quantify the adjusted odds ratios (aORs) for the relationship between each air pollutant and oral clefts while controlling for key covariates. Using monthly averages, a cleft lip with or without cleft palate (CLP) was associated with PM2.5 (aORs 2nd month = 1.34, CI:1.19–1.49; aORs 3rd month=1.14, CI:1.02–1.28), PM10 (aORs 2nd month = 1.11, CI:1.00–1.23) and CO (aORs 2nd month = 1.31, CI:1.14–1.51; aORs 3rd month = 1.17, CI:1.03–1.33). A cleft palate only (CPO) was associated with PM2.5 (aORs 2nd month = 1.24, CI: 1.03–1.48), and O3 (aORs 2nd month = 1.21, CI: 1.03–1.42; aORs 3rd month = 1.18, CI: 1.02–1.37). Our findings reveal an association between air pollutants exposure and the risk of oral clefts. Future studies are needed to confirm these associations, and clarify the causality related to specific pollutants during the most relevant vulnerable exposure time windows for oral clefts during pregnancy.