Subtle Alterations of Tidal Breathing Variables in Healthy Late Preterm Neonates at Term‐Equivalent Age

ABSTRACT Background Late‐preterm birth is associated with increased respiratory morbidity, but tidal breathing at term‐equivalent age remains incompletely characterized. We hypothesized that healthy late‐preterm neonates would differ from term neonates, with the between‐group difference in t PTEF /t E designated as the primary outcome. Methods In this prospective cross‐sectional study, 60 healthy late‐preterm and 60 term neonates underwent tidal breathing analysis (MasterScreen PAED) at term‐equivalent age (40 weeks’ postmenstrual age) during natural quiet sleep without sedation. Results Late‐preterm neonates had lower t PTEF /t E (27.4 ± 7.0% vs. 31.2 ± 6.9%; Benjamini–Hochberg‐adjusted p = 0.028; Cohen's d = 0.544) and V PTEF / V E [28.6 (25.1–31.0)% vs. 32.1 (27.3–35.5)%; adjusted p = 0.028; Cliff's δ = 0.304] than term neonates. Respiratory rate was higher (53.2 ± 9.1 vs. 49.6 ± 9.5 breaths/min), but not significant after correction (adjusted p = 0.126). No other tidal breathing variables differed significantly after correction. In the primary multivariable model, each additional week of exact gestational age was associated with a 1.18‐percentage‐point increase in t PTEF /t E after adjustment for sex, body weight, and crown–heel length (B = 1.182; 95% CI, 0.540–1.823; β = 0.323; p < 0.001). When postnatal age replaced gestational age, the association was inverse (B = −0.167/day; 95% CI, −0.263 to −0.071; β = −0.306; p < 0.001). Conclusion At term‐equivalent age, healthy late‐preterm neonates had modestly lower t PTFEF /t E and V PTEF / V E than term neonates. These findings may reflect subtle maturational differences in expiratory flow dynamics associated with late‐preterm birth.