Background: Moderate-to-late preterm (MLP) birth (32- <37 weeks of gestational age) has been associated with impaired lung function in adolescence, but data in adulthood and physiologic phenotyping beyond spirometry are scarce. We aimed to investigate lung function development from adolescence into young adulthood, and to provide physiologic phenotyping in individuals born MLP.  

Methods: Lung function data from individuals born MLP (n=110) and term (37-<42 weeks of gestational age, n=1895) in the Swedish birth cohort BAMSE were used for analysis and included dynamic spirometry, fractional exhaled nitric oxide, and multiple breath nitrogen wash-out. Data from 16- and 24-year follow-ups were analysed using regression models stratified on sex and adjusted for smoking. Data-driven latent class analysis was used to phenotype MLP individuals at 24 years, and groups were related to background factors.  

Results: Males born MLP had lower FEV1 at 24 years of age (-0.28 z-score, p=0.045) and FEV1/FVC-ratio (-0.38 z-score, p=0.01), when compared to males born at term. In females, no difference was seen at 24 years, partly explained by a significant catch-up in FEV1 between 16 and 24 years (0.18 z-score, p=0.01). The latent lung function phenotypes described as ?asthma-like?, ?dysanapsis? and ?normal preterm? were identified within the preterm group. Maternal overweight in early pregnancy was associated with ?asthma-like? group membership (OR 3.59, p=0.02).   

Conclusion: Our results show impaired FEV1 and FEV1/FVC at peak lung function in males born MLP, while females born MLP had significant catch-up between the ages of 16 and 24 years. Several phenotypes of lung function impairment exist in individuals born MLP.