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

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.

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 [FEF_25-75%]) 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 22^nd of September 2021 to the 29^th 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).

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] I²) 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 FEF_25-75%: -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] I²) 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 FEF_25-75%: -0.33 [-0.54 to -0.20] 94.7%.

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.

This work is supported by grants from the National Health and Medical Research Council (Centre of Research Excellence #1153176, Project grant #1161304); Medical Research Future Fund (Career Development Fellowship to J.L.Y Cheong #1141354) and from the Victorian Government's Operational Infrastructure Support Programme. C. Du Berry's PhD candidature is supported by the Melbourne Research Scholarship and the Centre of Research Excellence in Newborn Medicine.