Introduction:We investigated the association between tidal breathing lung function at 6 weeks of age and virus bronchiolitis hospitalisation in the first year of life.Methods: Infants born to mothers with asthma in pregnancy from the Breathing for Life Trial were assessed at 6 weeks of age and tidal breathing parameters we measured including time to reach peak tidal expiratory flow as a percentage of total expiratory time(tPTEF:tE%).Electronic medical records were accessed to extract verified hospital admissions for bronchiolitis in the first year of life. Associations were investigated using tPTEF:tE% quartiles and calculating the trend between the groups using multivariate logistic regression models and the Chi-squared test.Results:Infants hospitalised for bronchiolitis up to 12 months of age (n=22) were compared with non-hospitalised infants(n=364). In the multivariate logistic regression models, children with lower levels of tPTEF:tE% at 6 weeks were at a significantly higher risk for being admitted to the hospital for bronchiolitis (adjusted odds ratio for lowest quartile [aOR] 3.59, p-value for trend=0.035). Risk factors for bronchiolitis also included prematurity(aOR 30.7, p-value<0.001), having older siblings (aOR 9.45, p-value<0.0001), and a maternal BMI in pregnancy of 30kg/m2 or greater (aOR 8.90, p-value=0.023).Conclusion: Lower lung function at six weeks of age is associated with increased risk to bronchiolitis hospital admission in the first year of life.Future research is required to explore whether the prioritisation of infants for RSV immunisation due to lower lung function is cost-effective.