Background: Rates of preterm birth have increased in most industrialised countries but data on later lung function of late preterm births are limited. A study was undertaken to compare lung function at 8-9 and 14-17 years in children born late preterm (33-34 and 35-36 weeks gestation) with children of similar age born at term (≥37 weeks gestation). Children born at 25-32 weeks gestation were also compared with children born at term.
Methods: All births from the Avon Longitudinal Study of Parents and Children (n=14 049) who had lung spirometry at 8-9 years of age (n=6705) and/or 14-17 years of age (n=4508) were divided into four gestation groups.
Results: At 8-9 years of age, all spirometry measures were lower in the 33-34-week gestation group than in controls born at term but were similar to the spirometry decrements observed in the 25-32-week gestation group. The 35-36-week gestation group and term group had similar values. In the late preterm group, at 14-17 years of age forced expiratory volume in 1 s (FEV(1)) and forced vital capacity (FVC) were not significantly different from the term group but FEV(1)/FVC and forced expiratory flow at 25-75% FVC (FEF(25-75%)) remained significantly lower than term controls. Children requiring mechanical ventilation in infancy at 25-32 and 33-34 weeks gestation had in general lower airway function (FEV(1) and FEF(25-75)) at both ages than those not ventilated in infancy.
Conclusions: Children born at 33-34 weeks gestation have significantly lower lung function values at 8-9 years of age, similar to decrements observed in the 25-32-week group, although some improvements were noted by 14-17 years of age.