Associations of prenatal glyphosate exposure with child neurodevelopment in a Canadian pregnancy cohort study

Glyphosate is the most widely used pesticide worldwide. Few epidemiologic studies have examined the potential for neurotoxicity by glyphosate or its degradate, Aminomethylphosphonic Acid (AMPA). We examined associations of maternal urinary glyphosate and AMPA concentrations with child cognitive, social, and behavioural functioning in participants enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study.

Maternal urinary glyphosate and AMPA concentrations were measured in first trimester spot urine samples. We assessed children's cognition (IQ) at 3-4 years of age (n = 572) using the Wechsler Preschool and Primary Scale of Intelligence-III. Social (n = 566) and behavioural (n = 840) functioning were assessed using parent-report versions of the Social Responsiveness Scale-2 and Behavioral Assessment System for Children-2. We quantified associations between maternal urinary glyphosate and AMPA concentrations and child neurodevelopmental outcomes using multivariable linear regression models and assessed effect modification by child sex, maternal folic acid, and plasma folate.

Median (IQR) urinary glyphosate and AMPA concentrations were 0.31 (0.33) μg/L and 0.25 (0.25) μg/L. Maternal urinary glyphosate and AMPA concentrations were not significantly associated with children's cognitive, social or behavioural functioning, and there was no evidence of effect modification. We found a non-significant inverse trend between maternal urinary AMPA concentrations and Performance IQ (B = -0.85; 95 %CI: -1.71,0.01).

In this primarily urban cohort of Canadian mother-child pairs, prenatal glyphosate and AMPA exposure were not significantly associated with child neurodevelopment. Further evaluation of glyphosate as a potential developmental neurotoxicant in a study with multiple urine samples per participant and at higher exposure levels is warranted.