1. Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway
2. Department of Non-communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, England
3. School of Epidemiology and Public Health, University of Ottawa, Ottawa, Ontario, Canada
4. Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada
5. Department of Infectious Disease, Norwegian Institute of Public Health, Oslo, Norway
6. Department of Health Management and Health Economics, Institute of Health and Society, University of Oslo, Oslo, Norway