1. Department of Obstetrics & Gynecology, McMaster University, Hamilton, Ontario, Canada;
2. Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba, Canada;
3. School of Epidemiology, Public Health and Preventive Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada;
4. Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada;
5. Department of Paediatrics, University of Toronto and the Hospital for Sick Children, Toronto, Ontario, Canada;
6. Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada;
7. Maternal, Child and Youth Health Surveillance and Epidemiology Division, Centre for Chronic Disease Prevention, Public Health Agency of Canada, Ottawa, Ontario, Canada