1. Centre for Fertility and Health, Norwegian Institute of Public Health , Oslo , Norway
2. Public Health Ontario , Toronto , Canada
3. ICES , Toronto , Canada
4. Dalla Lana School of Public Health, University of Toronto , Toronto , Canada
5. Centre for Vaccine Preventable Diseases, University of Toronto , Toronto , Canada
6. Department of Family and Community Medicine, University of Toronto , Toronto , Canada
7. University Health Network , Toronto , Canada
8. School of Epidemiology and Public Health, University of Ottawa , Ottawa , Canada
9. Children's Hospital of Eastern Ontario Research Institute , Ottawa , Canada