1. School of Epidemiology and Public Health, Faculty of Medicine University of Ottawa Ottawa Ontario Canada
2. Department of Community Health and Epidemiology Dalhousie University Halifax Nova Scotia Canada
3. Department of Obstetrics and Gynecology, Faculty of Medicine and Health Sciences Université de Sherbrooke, and the Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CRCHUS) Sherbrooke Quebec Canada