The Effect of Being Born Moderate-to-Late Preterm on Lung Function and Respiratory Morbidity at 9 to 10 Years of Age.

Rationale: The effect of moderate-late preterm (MLP; 32 to 36 completed weeks' gestation) birth on childhood respiratory health is unclear. Objectives: To assess the effect of being born MLP, compared with being born at term (≥37 completed weeks' gestation), on lung function and respiratory morbidity at 9-10 years of age. Methods: Prospective cohort of children born MLP or at term at the Royal Women's Hospital, Victoria, Australia. Participants completed pre- and post-bronchodilator spirometry, DL_CO, plethysmography, and multiple breath washout at 9-10 years of age. Parents completed the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Mean differences in z-scores of lung function outcomes and risk ratio (RR) for ISAAC outcomes between those born moderate-late preterm and those born at term were estimated using regression models with adjustment for potential confounding. Multiple imputation was used to handle missing data. Measurements and Main Results: 148 of 201 children born MLP and 120 of 201 term-born controls were assessed at 9-10 years. Compared with controls, children born moderate-late preterm had lower mean z-scores (mean difference, 95% confidence interval) for FEV₁: -0.35, (-0.61, -0.08), FEV₁/FVC: -0.29, (-0.58, -0.01), FEF_25-75%: -0.33, (-0.62, -0.04) and DL_CO: -0.24, (-0.45, -0.03). Participants born MLP had higher risk of experiencing asthma symptoms (RR, 95% CI: 1.52 [1.08, 2.14]). Conclusions: Children born MLP have lower lung function and increased risk of exhibiting asthma symptoms compared with term-born peers at 9-10 years. Such findings at the end of the first decade of life may portend adverse consequences for respiratory health in adulthood.