1. MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrooke’s Hospital, P.O. Box 285, Cambridge CB2 0QQ, UK
2. Department of Epidemiology, Groningen University, 9700 RB Groningen, The Netherlands
3. Section of Neonatal Medicine, Department of Medicine Chelsea and Westminster Hospital Campus, Imperial College London, London SW10 9NH, UK
4. Department of Paediatrics, University of Cambridge, Addenbrooke’s Hospital, P.O. Box 116, Cambridge CB2 0QQ, UK