Associations between Prenatal Exposure to Perchlorate, Thiocyanate, and Nitrate and Child Neurodevelopment in the...

Associations between prenatal exposure to perchlorate, thiocyanate, and nitrate and autism spectrum disorder (ASD) remain largely unexplored. We investigated these associations in the MARBLES cohort, a prospective cohort with an elevated familial likelihood of ASD. A total of 310 mothers provided 1916 urine samples during pregnancy, and their children were classified at age 3 years as typically developing (TD), ASD, or non-TD (developmental concerns not meeting ASD diagnostic criteria). We estimated relative risks for ASD and non-TD compared with TD using Poisson regression and assessed mixture effects using quantile G-computation and Bayesian kernel machine regression. Overall and mixture analyses showed no significant associations between prenatal exposure to these NIS inhibitors and the child neurodevelopmental outcomes. However, stratified analyses identified several context-specific associations according to child sex, trimester of exposure, maternal urinary iodine concentration, and passive smoking status, some of which remained significant after false-discovery-rate correction. These findings suggest that susceptibility to prenatal exposure to perchlorate, thiocyanate, and nitrate may vary across population subgroups and exposure windows. Although these subgroup-specific associations should be considered hypothesis generating, they highlight the need for future studies integrating thyroid biomarkers and mechanistic approaches to better understand thyroid-related pathways underlying child neurodevelopment.