1. Department of Global Public Health and Primary Care; University of Bergen; Bergen Norway
2. National Institute of Environmental Health Sciences; Epidemiology Branch; Durham NC
3. Department of Obstetrics and Gynecology; Haukeland University Hospital; Bergen Norway
4. Tornblad Institute; University of Lund; Lund Sweden
5. Department of Obstetrics and Gynecology; Institute for the Health of Women and Children; Sahlgrenska University Hospital; Göteborg Sweden