Background: Congenital heart defects may be environmentally related, but the association with elevated ambient temperature has received little attention.
Objectives: We studied the relationship between outdoor heat during the first trimester of pregnancy and risk of congenital heart defects.
Methods: We carried out a retrospective cohort study of 704,209 fetuses between 2 and 8 weeks postconception from April to September in Quebec, Canada, 1988–2012. We calculated the prevalence of congenital heart defects at birth according to the number of days women were exposed to maximum temperature ≥ 30°C. In log-binomial regression models, we estimated prevalence ratios (PR) and 95% confidence intervals (CI) for the relationship of temperature with seven critical and eight noncritical heart defects, adjusted for pregnancy characteristics.
Results: Prevalence of congenital heart defects was 979.5 per 100,000 for 10 days or more of temperature ≥ 30°C compared with 878.9 per 100,000 for 0 days of exposure. Temperature was more precisely associated with noncritical than critical defects, which had lower prevalence. Fetuses exposed to 15 days of temperature ≥ 30°C between 2 and 8 weeks postconception had 1.06 times the risk of critical defects (95% CI: 0.67, 1.67) and 1.12 times the risk of noncritical defects (95% CI: 0.98, 1.29) relative to 0 days. Associations were higher for atrial septal defects (PR 1.37, 95% CI: 1.10, 1.70) than for other noncritical defects. For atrial septal defects, associations with elevated temperatures began the 3rd week postconception.
Conclusions: Extreme heat exposure during the first trimester may be associated with noncritical heart defects, especially of the atrial septum.
1University of Montreal Hospital Research Centre, Montreal, Quebec, Canada; 2Institut national de santé publique du Québec, Montreal, Quebec, Canada; 3University of Sherbrooke Hospital Research Centre, Sherbrooke, Quebec, Canada; 4Departments of Pediatrics and Community Health Sciences, Cummings School of Medicine, University of Calgary, Calgary, Alberta, Canada; 5National Collaborating Centre for Environmental Health, British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada
Recommended Citation:
Nathalie Auger,1,2 William D. Fraser,et al. Risk of Congenital Heart Defects after Ambient Heat Exposure Early in Pregnancy[J]. Environmental Health Perspectives,2017-01-01,Volume 125(Issue 1):8