1. Faculty of Medicine, University of Oslo Oslo Norway
2. Institute of clinical medicine, Faculty of Medicine, University of Oslo Oslo Norway
3. Department of Paediatric and Adolescent Medicine Drammen Hospital Drammen Norway
4. Department of Paediatric and Adolescent Medicine Haukeland University Hospital Bergen Norway
5. Department of Neonatal Intensive Care, Division of Paediatric and Adolescent Medicine Oslo University Hospital Oslo Norway