1. Clinical Biostatistics Unit. Ramón y Cajal Hospital (IRYCIS). Francisco de Vitoria University (UFV Madrid). CIBER Epidemiology and Public Health (CIBERESP); Cochrane Collaborating Centre; Carretera de Colmenar Km 9.100 Madrid Spain 28034
2. Ramon y Cajal Institute for Health Research (IRYCIS), CIBER Epidemiology and Public Health (CIBERESP), Madrid (Spain) and Queen Mary University of London; Clinical Biostatistics Unit; Ctra. Colmenar km 9,100 Madrid Madrid Spain 28034
3. Dartmouth-Hitchcock Medical Center; Department of Pediatrics, Neonatal Division; One Medical Center Drive Lebanon NH USA 03576-001
4. Hospital Ramon y Cajal; Pediatric Cardiology Unit; Madrid Spain
5. Barts and The London School of Medicine and Dentistry, Queen Mary University of London; Centre for Primary Care and Public Health; 58 Turner Street London UK E1 2AB
6. University of Birmingham; School of Clinical and Experimental Medicine; Birmingham Women's Hospital Edgbaston Birmingham UK B15 2TT