1. Department of Pediatrics, Turku University Hospital, Turku, Finland;
2. National Institute for Health and Welfare, Helsinki, Finland;
3. Department of Pediatrics, Hospital for Children and Adolescents, Helsinki, Finland;
4. Department of Pediatrics, Oulu University Hospital, Oulu, Finland; and
5. Department of Pediatrics, Tampere University Hospital, Tampere, Finland