Urban environment during pregnancy, cognitive abilities, motor function, and externalizing and internalizing symptoms at 2-5 years old in 3 Canadian birth cohorts

Background: More than 80% of the Canadian population lives in urban settings. Urban areas usually bring exposure to poorer air quality, less access to green spaces, and higher building density. These environmental factors may endanger child development.

Objective: To assess the relationship of urban environmental exposures during pregnancy with cognitive abilities, motor function, externalizing and internalizing symptoms in children.

Method: We included 6,279 mother-child pairs from 3 Canadian population-based birth-cohorts (3D Cohort Study in Montreal, Quebec City, and Sherbrooke, AOF Study in Calgary, CHILD Study in Edmonton, Vancouver, Toronto, and Winnipeg). We estimated 7 environmental exposures of the built environment, surrounding greenness, and air pollution, around participant's home addresses during pregnancy. Validated neuropsychological tests were used to assess non-verbal and verbal abilities, gross and fine motor function, externalizing and internalizing symptoms at child's age 2 to 5 years. We assessed associations of each environmental exposure indicator with each of the 6 outcomes, using multivariate linear regression models. We conducted analyses separately by city of recruitment and combined estimates in meta-analyses.

Results: Overall, urban environment during pregnancy was not associated with cognitive abilities (e.g., -0.81 non-verbal points 95 %CI [-2.10; 0.48] per 1 μg/m³ increase in PM_2.5), motor function, or externalizing and internalizing symptoms. In individual cohorts, we found associations of some environmental exposures, in particular building density, fine particles, and nitrogen dioxide with non-verbal abilities, verbal abilities, and fine motor function, but overall confidence intervals in the meta-analyses included the null.

Conclusion: We found no evidence of a relationship of prenatal built environment, surrounding greenness, and air pollution with cognitive abilities, motor functions or externalizing and internalizing symptoms in childhood. Urban environment has been shown to influence health across the lifecourse, however, specific exposures during pregnancy do not seem associated with poorer neurodevelopment in children of 2- to 5- year.