Prenatal exposure to organophosphate esters and child cognitive development in the MARBLES prospective cohort.

BACKGROUND: Epidemiological studies on prenatal exposure to organophosphate esters (OPEs) and child cognitive development remain inconclusive. We examined associations between prenatal maternal urinary OPE biomarker concentrations and child cognitive development assessed at multiple time points. METHODS: The study included 311 mother-child pairs from MARBLES, a prospective cohort of children with elevated familial likelihood of autism and at least one available cognitive assessment. We quantified nine OPE biomarkers in one maternal urine sample per participant, collected predominantly during the third trimester. Cognitive development was assessed at 6, 12, 24, and 36 months, with observations at each time point included in the primary analyses. We examined associations between specific gravity-adjusted urinary OPE biomarker concentrations, both individually and as a mixture, and MSEL Composite and subscale scores at each time point. We also evaluated child sex as an effect modifier and assessed longitudinal changes in scores across assessments. RESULTS: Associations between individual prenatal OPE biomarkers and child cognitive outcomes were largely null after correction for multiple comparisons. Associations between bis(2-chloroethyl) phosphate (BCETP) concentrations and Composite and Visual Reception scores differed by age across assessments, with scores appearing higher at 36 months. Trajectory analyses identified no associations. Effect modification by child sex was not observed. CONCLUSIONS: We did not observe that prenatal OPE exposure was associated with cognitive development across infancy and toddlerhood; however, we observed that associations differed by age at assessment, highlighting the importance of repeated outcome measurements. Larger studies in general-population cohorts with repeated exposure measurements throughout pregnancy are warranted.