Study population
The CHILD Cohort Study is a Canadian birth cohort consisting of 3455
children and their parents.(18,19) Mothers were initially recruited
during the second or third trimesters of pregnancy from four provinces
across Canada: British Columbia (Vancouver), Alberta (Edmonton),
Manitoba (Winnipeg, Morden and Winkler), and Ontario (Toronto). Their
children have been followed from birth onwards, with a home visit at 3-4
months of age, repeated questionnaire surveys examining environmental
exposures, and clinic visits for detailed assessments and obtaining
biospecimens (e.g., blood, stool, urine, nasal swabs) at ages 1, 3, and
5 years.(19–21) Written informed consent was obtained from the parents
of children enrolled in this study. Protocols were approved by the Human
Research Ethics Boards at Queen’s University, McMaster University, the
Hospital for Sick Children, and the Universities of Manitoba, Alberta,
and British Columbia.