1. INSERM, UMR S149, IFR 69, Unit on Perinatal and Women's Health, Hôpital Tenon, Paris, France
2. Université Pierre et Marie Curie-Paris 6, Paris, France
3. National Perinatal Epidemiology Unit, University of Oxford, Oxford, United Kingdom
4. Department of Paediatrics, University of Nottingham, Nottingham, United Kingdom
5. Barts and the London, Queen Mary's School of Medicine and Dentistry, University of London, London, United Kingdom