History and Symptoms
Neonatal and maternal health data was obtained from medical records and the KEMH neonatal database. Respiratory symptoms history was obtained using validated general and respiratory questionnaires adapted from the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaires.27 Respiratory symptoms such as wheeze, shortness of breath, cough and rattly chest in the 3 months prior to the participant’s study visit were parentally or self-reported, as appropriate.