Pesticides in pregnancy and autism traits: a big study finds no link

Researchers measured organophosphate pesticide breakdown products in the urine of 3,339 pregnant women across 20 US sites and later scored their children's autism-related traits. After full adjustment, prenatal exposure showed no association with those traits.

Organophosphate pesticides are known neurotoxins, and most Americans get low-level exposure through food, so the worry that prenatal exposure might contribute to autism has circulated for years with inconsistent evidence behind it. This analysis pooled harmonized data from 20 study sites in the US ECHO cohort, following mother-child pairs recruited between 1997 and 2019. Scientists measured two markers of organophosphate exposure in the mothers' urine during pregnancy: TCPy and the sum of six dialkyl phosphate metabolites. Years later, parents rated their children on the Social Responsiveness Scale, a standard measure of autism-related traits, at an average age of 6.4 years. Among the 3,339 pairs, crude models actually hinted at slightly lower autism trait scores with higher exposure, but once the researchers adjusted for maternal demographics, behavior, and diet, the associations shrank to nothing, for example a beta of -0.13 (95% CI -0.57 to 0.31) per doubling of TCPy. Results held across boys and girls and across several alternative statistical approaches, and diet quality did not change the picture. Limitations worth noting: exposure came from spot urine samples, which reflect recent intake rather than a whole pregnancy, autism traits were parent-reported rather than clinically diagnosed, and the exposure range studied was typical dietary levels, not occupational ones.