1. Department of Global Public Health and Primary Care University of Bergen Bergen Norway
2. Centre for Fertility and Health Norwegian Institute of Public Health Oslo Norway
3. Norwegian Research Centre for Women's Health Oslo University Hospital, Rikshospitalet Oslo Norway
4. Department of Clinical Science University of Bergen Bergen Norway
5. Department of Obstetrics and Gynecology Haukeland University Hospital Bergen Norway
6. Division for Mental and Physical Health Norwegian Institute of Public Health Bergen Norway
7. Epidemiology Branch National Institute of Environmental Health Sciences Durham North Carolina USA