1. Sahlgrenska School of Public Health and Community Medicine, Section of Primary Health Care, University of Gothenburg, Box 454, 405 30 Gothenburg, Sweden
2. The Queen Silvia Children's Hospital, Göteborg, Paediatric Growth Research Centre, Department of Paediatrics, The Sahlgrenska Academy at University of Gothenburg, Smörslottsgatan, 41685 Gothenburg, Sweden