1. Department of Obstetrics and Gynecology; Rigshospitalet; University of Copenhagen; Copenhagen Denmark
2. Department of Obstetrics and Gynecology; Holbaek Hospital and University of Copenhagen; Copenhagen Denmark
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 Obstetrics and Gynecology; Landspitali University Hospital; Reykjavik Iceland
6. Department of Obstetrics and Gynecology; Clinical Sciences Lund; Lund University; Lund Sweden
7. Department of Obstetrics and Gynecology; University Hospital; Helsinki Finland
8. Department of Obstetrics and Gynecology; Haukeland University Hospital; Bergen Norway
9. Department of Obstetrics and Gynecology; Karolinska University Hospital; Huddinge Sweden
10. National Board of Health and Welfare; Stockholm Sweden
11. THL; National Institute for Health and Welfare; Helsinki Finland
12. Nordic School of Public Health; Gothenburg Sweden