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 to late preterm (MLP) birth (32–36 completed weeks’ gestation) 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: A prospective cohort study was conducted among children born MLP or at term at the Royal Women’s Hospital (Victoria, Australia). Participants completed pre and postbronchodilator spirometry, measurement of diffusing capacity of the lung for carbon monoxide, plethysmography, and multiple-breath washout at 9–10 years of age. Parents completed the ISAAC (International Study of Asthma and Allergies in Childhood) questionnaire. Mean differences in z-scores of lung function outcomes and risk ratio for ISAAC outcomes between those born MLP and those born at term were estimated using regression models with adjustment for potential confounding. Multiple imputation was used to handle missing data. Results: A total of 148 of 201 children born MLP and 120 of 201 term-born control subjects were assessed at 9–10 years. Compared with control subjects, children born MLP had lower mean z-scores for forced expiratory volume in 1 second (mean difference, 20.35 [95% confidence interval (CI), 20.61 to 20.08]), ratio of forced expiratory volume in 1 second to forced vital capacity (mean difference, 20.29 [95% CI, 20.58 to 20.01]), forced expiratory flow at 25–75% of forced vital capacity (20.33 [95% CI, 20.62 to 20.04]), and diffusing capacity of the lung for carbon monoxide (20.24 [95% CI, 20.45 to 20.03]). Participants born MLP had higher risk of experiencing asthma symptoms (risk ratio, 1.52 [95% CI, 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.