Queen Mary University of London - Blizard Institute, University of Copenhagen - Copenhagen Prospective Study on Asthma in Childhood (COPSAC), University of Copenhagen - Copenhagen Prospective Study on Asthma in Childhood (COPSAC), University of Southampton - Medical Research Council Life Course Epidemiology Unit, University of Southampton, University of Southampton - Medical Research Council Life Course Epidemiology Unit, University of Rochester, University of Southampton, University of Toronto - The Hospital for Sick Children - SickKids, University of Auckland, Harvard Medical School - Channing Division of Network Medicine and Queen Mary University of London - Barts and The London School of Medicine and Dentistry