Association of maternal urinary pesticide metabolites with neonatal birth outcomes and the moderating effects of iodine

Previous studies have demonstrated the effects of prenatal pesticide exposure on birth outcomes. How to mitigate the harmful effects of pesticide exposure is of great practical significance. The micronutrient iodine is a cornerstone for the growth and development of newborns and throughout their lifespan. In this study, we investigated the association of urinary pesticide metabolite and urinary iodine concentrations with neonatal birth weight, birth length, and ponderal index in 781 mother-newborn pairs. The indirect role of urinary iodine in the associations between urinary pesticide metabolites and neonatal birth indicators was assessed by moderation analysis. The geometric mean concentration of total pesticide metabolites was 10.32 mu g/L and the median urinary iodine concentration was 192.63 mu g/L among the pregnant women. The mean birth length and birth weight of the newborns were 49.82 cm and 3186.94 g, respectively. Restricted cubic spline analysis revealed significant non-linear associations of 2,4-dichlorophenoxyacetic acid and Trans-dichlorovinyldimethylcyclopropane carboxylic acid with birth weight. The Bayesian kernel-machine regression analysis did not show a significant overall effect of mixed pesticide exposure on neonatal birth outcomes, suggesting that the effects of individual metabolites may be more critical than overall pesticide exposure. The moderation analysis results showed that the impact of pesticide metabolites on the ponderal index varied from a significant negative to a non-significant or significant positive correlation as urinary iodine concentrations increased. The results demonstrated that ensuring adequate iodine levels may help mitigate the adverse effects of pesticide exposure on birth outcomes.