1. Section of Obstetrics; Department for Women's and Children's Health; Oslo University Hospital; Oslo Norway
2. Department of Public Health and General Practice; Faculty of Medicine; The Norwegian University of Science and Technology; Trondheim Norway
3. Department of Obstetrics and Gynaecology; St Olavs Hospital; Trondheim University Hospital; Trondheim Norway
4. National Resource Centre for Women's Health; Department for Women's and Children's Health; Oslo University Hospital; Oslo Norway
5. Department of Health; Nutrition and Management; Faculty of Health Sciences; Oslo and Akershus University College of Applied Sciences; Oslo Norway