Prenatal Exposure to Phthalates and Cognitive Outcomes in Early Childhood in the Apron Cohort

Background/Aim: Phthalates are ubiquitous endocrine disrupting chemicals. Previous research suggests an association between prenatal maternal phthalate levels and adverse behavioural outcomes in children. However, no studies have investigated the association between prenatal phthalate exposure levels and cognitive outcomes in children 3 to 4 years of age.Methods: Twelve urinary phthalate metabolites were measured in urine collected in the second trimester from 416 women enrolled in the Alberta Pregnancy Outcomes and Nutrition (APrON) Study. Cognitive outcomes (IQ) of the children of these women were assessed at 3 to 4 years of age using the Wechsler Preschool and Primary Scale of Intelligence – Fourth Edition (WPPSI-IV). Associations between prenatal phthalate concentrations and children’s cognitive outcomes were estimated using linear regression models.Results: Of the twelve urinary phthalate metabolites measured, eight metabolites showed statistically significant findings. After adjusting for gestational age, birth weight, maternal ethnicity, and maternal education, higher concentrations of both low molecular weight phthalate metabolites (miBP and mMP) and high molecular weight phthalate metabolites (mEHHP and mEHP) were associated with lower Full Scale IQ. Analyses of the WPPSI-IV subscales revealed that higher concentrations of the mBzP, mCOP, mECPP, and mNP metabolites were associated with lower scores on Working Memory, Fluid Reasoning, Visual Spatial and Verbal Comprehension subscales of the WPPSI-IV.Conclusions: Higher prenatal maternal urinary metabolite concentrations of both low and high molecular weight phthalates were associated with poorer cognitive outcomes in children at 3 to 4 years of age. As phthalate exposures are widespread in the Canadian environment, these findings are of public health significance.