1. Department of Obstetrics and Gynecology Akershus University Hospital Lørenskog Norway
2. Department of Obstetrics and Gynecology Haukeland University Hospital Bergen Norway
3. Department of Clinical Science University of Bergen Bergen Norway
4. Department of Pediatric Research University of Oslo Oslo Norway
5. Ann and Robert H. Lurie Children's Hospital of Chicago Chicago Illinois USA
6. Institute of Clinical Medicine, University of Oslo Oslo Norway