In utero pyrethroid pesticide exposure in relation to autism spectrum disorder (ASD) and other neurodevelopmental outcomes at 3 years in the MARBLES longitudinal cohort

Background: We assessed the relationships between prenatal pyrethroid pesticide exposure and autism spectrum disorders (ASD) or non-typical development (non-TD) at 3 years. Methods: Participants were mother-child pairs (n = 201) in the MARBLES (Markers of Autism Risk in Babies Learning Early Signs) cohort. Because familial recurrence risk is high, MARBLES enrolls pregnant women with a family history of ASD. Children from these pregnancies were clinically assessed at 3 years of age and classified into 3 outcome categories: ASD, typically developing (TD), or non-TD (neither TD or ASD). Repeated maternal second and third trimester urine samples were analyzed for pyrethroid metabolite 3-phenoxybenzoic acid (3PBA). Multinomial logistic regression was used to obtain relative risk ratios (RRR) linking 3-PBA concentrations averaged across each trimester and over pregnancy with child?s outcome: ASD or non-TD vs. TD. Models were adjusted for specific gravity, maternal pre-pregnancy BMI, prenatal vitamin use, birth year, home-ownership, and pregnancy concentrations of TCPy (3,5,6-trichloro-2-pyridinol, a metabolite of chlorpyrifos). Results: The median specific gravity corrected 3-PBA concentration of all samples was 1.46 ng/mL. Greater second trimester 3-PBA concentrations were associated with a relative risk ratio (RRR) for ASD of (RRR: 1.50 (95% CI 0.89 to 2.51), p = 0.12). There were no differences between non-TD and TD. Conclusions: This study found no evidence for differences in 3-PBA comparing non-TD with TD. A modestly elevated RRR was found comparing second trimester urinary 3-PBA concentrations for ASD versus TD; however, the confidence interval was wide and hence, these findings cannot be considered definitive.

Automated summary

This study found some trends in the relationship between prenatal pyrethroid pesticide exposure and autism spectrum disorders or non-typical development, but did not reach definitive conclusions.