1 Centre for Fertility and Health, Norwegian Institute of Public Health, P.O. Box 222 Skøyen, 0213 Oslo, Norway. Electronic address: [email protected].
2 Department of Public Health, University of Copenhagen, Copenhagen, Denmark.
3 Clinical Epidemiology Division, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden; Department of Obstetrics and Gynaecology, Visby County Hospital, Visby, Sweden.
4 Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway; Department of Non-communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom.
5 Clinical Epidemiology Division, Department of Medicine, Solna, Karolinska Institute, Stockholm, Sweden; Department of Women's Health, Karolinska University Hospital, Solna, Stockholm, Sweden.
6 Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway; Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.