Maternal exposure to ambient air pollution and risk of congenital limb defects in offspring

Limited evidence on exposure to maternal air pollutants before and after conception and the risk of congenital limb defects (CLDs) in offspring is inconsistent. We explored the dose‒response relationship between maternal air pollutant exposure before and after conception and the risk of CLDs and their subtypes and further examined whether individual sociodemographic characteristics modify these associations. We carried out a population-based cohort study in Wuhan, China, based on the government registration system. The CLDs and daily air pollutant concentration data were collected. Individual exposure was assessed via the inverse distance weighting method on the basis of maternal residential addresses. Multivariate logistic regression models were applied to evaluate the relationship between maternal exposure to air pollutants and the risk of CLDs, adjusting for covariates. A total of 1,864 infants were diagnosed with CLD, with an incidence of 3.7/1,000. Maternal exposure to SO2 in the first, second and third month of conception significantly increased the risk of overall CLDs, with adjusted odd ratios (aORs) ranging from 1.033 to 1.043. However, no significant correlation was found between exposure to PM2.5, PM10, NO2, CO, or O3 and CLD risk. Significant links were found for SO2 exposure with polydactyly and limb shortening in the subgroup analyses. Several significant modifying effects of individual characteristics were also observed. This study confirmed that increased exposure to SO2 during the first three months after conception increased the risk of CLDs and their subtypes in offspring, and these associations were modified by individual characteristics.