Long-term expiratory airflow of infants born moderate-late preterm: A systematic review and meta-analysis

Background Moderate-late preterm (MLP; 32 to <37 weeks' gestation) birth is associated with reduced expiratory airflow during child, adolescent and adult years. However, some studies have reported only minimal airflow limitation and hence it is unclear if clinical assessment in later life is warranted. Our aim was to compare maximal expiratory airflow in children and adults born MLP with term-born controls, and with expected norms. Methods We systematically reviewed studies reporting z-scores for spirometric indices (forced expired volume in 1 second [FEV1], forced vital capacity [FVC], FEV1/FVC ratio and forced expiratory flow at 25-75% of FVC [FEF25-75%]) from participants born MLP aged five years or older, with or without a term-born control group from 4 databases (MEDLINE, CINAHL, Embase, Emcare). Publications were searched for between the 22nd of September 2021 to the 29th of September 2021. A meta-analysis of eligible studies was conducted using a random effects model. The study protocol was published in PROSPERO (CRD #42021281518). Findings We screened 4970 articles and identified 18 relevant studies, 15 of which were eligible for meta-analysis (8 with term-born controls and 7 without). Compared with controls, MLP participants had lower z-scores ( mean difference [95% confidence interval] I-2) for FEV1 : -0.22 [-0.35, -0.09] 49.3%, FVC: -0.23 [-0.4, -0.06] 71.8%, FEV1/FVC: -0.11 [-0.20 to -0.03] 9.3% and FEF25-75%: -0.27 [-0.41 to -0.12] 21.9%. Participants born MLP also had lower z-scores, on average, when compared with a z-score of 0 (mean [95% CI] I-2) for FEV1 : -0.26 [-0.40 to -0.11] 85.2%, FVC: -0.18 [-0.34 to -0.02] 88.3%, FEV1/FVC: -0.24 [-0.43 to -0.05] 90.5% and FEF25-75%: -0.33 [-0.54 to -0.20] 94.7%. Interpretation Those born MLP had worse expiratory airflows than those born at term, and compared with norms, although reductions were modest. Clinicians should be aware that children and adults born MLP may be at higher risk of obstructive lung disease compared with term-born peers. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd.