1. Department of Paediatric and Adolescent Medicine, Stavanger University Hospital, Norway
2. Department of Clinical Science, University of Bergen, Norway
3. Department of Public Health and Primary Care, KU Leuven, University of Leuven, Belgium
4. Department of Health Registry and Development, Norwegian Institute of Public Health, Norway
5. Centre for Fertility and Health, Norwegian Institute of Public Health, Norway
6. Section for Health Care Collaboration, Haukeland University Hospital, Norway
7. Department of Paediatric and Adolescent Medicine, Haukeland University Hospital, Norway