1. Norwegian National Advisory Unit on Breastfeeding; Oslo University Hospital; Oslo Norway
2. Department of Pediatric and Adolescents Medicine; Akershus University Hospital; Lørenskog Norway
3. Oslo Centre for Biostatistics and Epidemiology; Department of Biostatistics; University of Oslo; Oslo Norway
4. Division for Health Services; Norwegian Institute of Public Health; Oslo Norway
5. Institute of Health and Society; University of Oslo; Oslo Norway
6. Department of General Practice; Institute of Health and Society; Faculty of Medicine; University of Oslo; Oslo Norway
7. Institute of Clinical Medicine; University of Oslo; Oslo Norway
8. Department of Transplantation Medicine; Oslo University Hospital; Oslo Norway
9. General Practice Research Unit (AFE); Department of General Practice; Institute of Health and Society; University of Oslo; Oslo Norway