1. Department of Internal Medicine, Ringerike Hospital, Vestre Viken Hospital Trust, Hønefoss, Norway
2. Department of Surgery, Lillehammer Hospital, Innlandet Hospital Trust, Lillehammer, Norway
3. Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway
4. Medical Birth Registry of Norway, Norwegian Institute of Public Health, Bergen, Norway
5. Department of Clinical Science, University of Bergen, Bergen, Norway
6. Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway