Prenatal Organophosphate Exposure and Autism-Related Traits in Children

Importance: Organophosphate pesticides (OPs) are established neurotoxicants; prenatal OP exposure is widespread in the US population, primarily through diet. Evidence linking prenatal OP exposure to autism spectrum disorder (ASD) and autism-related traits remains inconsistent. Objective: To examine the association between prenatal OP exposure and autism-related traits in childhood and to assess potential differences in the association by child sex and maternal diet. Design, Setting, and Participants: This pooled prospective cohort study used harmonized data from mother-child pairs from 20 study sites in the Environmental influences on Child Health Outcomes (ECHO) cohort. Participants were recruited from January 1997 through December 2019, and autism-related outcomes were assessed in children ages 2 to 19 years. Data analysis was performed from April 2024 and November 2025. Exposure: Prenatal OP exposure using urinary concentrations of 3,5,6-trichloro-2-pyridinol (TCPy) and the sum of 6 dialkyl phosphate (ΣDAP) metabolites. Main Outcomes and Measures: Parents reported autism-related traits in children using the Social Responsiveness Scale (SRS). Multivariable linear, quantile, and logistic regression models were used to estimate associations between biomarkers and SRS T scores overall and by child sex, adjusting for maternal sociodemographic and behavioral factors. We further adjusted for dietary factors in additional models and tested effect modification by maternal diet quality in exploratory analyses. Results: Among 3339 mother-child pairs examined, mean (SD) maternal age was 31 (6) years, 1665 children (49.9%) were female, and the SRS was administered at a mean (SD) age of 6.4 (3.87) years. Crude or minimally adjusted models suggested inverse associations between prenatal TCPy or ΣDAP levels and SRS scores, but these associations attenuated and lost statistical significance after full adjustment (β per doubling of TCPy concentration [ng/mL] = -0.13; 95% CI, -0.57 to 0.31; β per doubling of ΣDAP [nmol/L] = -0.42; 95% CI, -1.03 to 0.19). Results were consistent across sex-stratified models, secondary analyses using quantile and logistic regressions, various sensitivity analyses, and after adjustments for dietary confounders. There was no evidence of effect modification by diet quality. Conclusions and Relevance: In this large, prospective cohort study among the ECHO cohort, prenatal OP exposure was not associated with autism-related traits in childhood. Given the known adverse impacts of pesticides in other contexts, further research should consider interactions with other factors, genetic susceptibility, higher exposures, or combined chemical mixtures.