1. Department of Paediatric Cardiology Oslo University Hospital Oslo Norway
2. Department of Paediatric and Adolescent Medicine, Sorlandet Hospital Kristiansand Norway
3. Department of Cardiology, Sorlandet Hospital Arendal Norway
4. Department of Obstetrics and Gynaecology, Fetal Medicine Unit Oslo University Hospital Oslo Norway
5. Oslo Centre of Biostatistics and Epidemiology, Research Support Services Oslo University Hospital Oslo Norway
6. Department of Neonatal Intensive Care Oslo University Hospital Oslo Norway
7. Institute of Clinical Medicine, University of Oslo Oslo Norway