Children Born Preterm at the Turn of the Millennium Had Better Lung Function Than Children Born Similarly Preterm in the Early 1990s

Abstract

Objective: Compare respiratory health in children born extremely preterm (EP) or with extremely low birthweight (ELBW) nearly one decade apart, hypothesizing that better perinatal management has led to better outcome.

Design: Fifty-seven (93%) of 61 eligible 11-year old children born in Western Norway in 1999-2000 with gestational age (GA) <28 weeks or birthweight <1000 gram (EP1999-2000) and matched term-controls were assessed with comprehensive lung function tests and standardized questionnaires. Outcome was compared with data obtained at 10 years of age from all (n = 35) subjects born at GA <29 weeks or birthweight <1001 gram within a part of the same region in 1991-92 (EP1991-1992) and their matched term-controls.

Results: EP1999-2000 had significantly reduced forced expiratory flow in 1 second (FEV1), FEV1 to forced vital capacity (FEV1/FVC) and forced expiratory flow between 25-75% of FVC (FEF25-75), with z-scores respectively -0.34, -0.50 and -0.61 below those of the term-control group, and more bronchial hyperresponsiveness to methacholine (dose-response-slope 13.2 vs. 3.5; p<0.001), whereas other outcomes did not differ. Low birthweight z-scores, but not neonatal bronchopulmonary dysplasia (BPD) or low GA, predicted poor outcome. For children with neonatal BPD, important lung-function variables were better in EP1999-2000 compared to EP1991-1992. In regression models, improvements were related to more use of antenatal corticosteroids and surfactant treatment in the EP1999-2000.

Conclusions: Small airway obstruction and bronchial hyperresponsiveness were still present in children born preterm in 1999-2000, but outcome was better than for children born similarly preterm in 1991-92, particularly after neonatal BPD. The findings suggest that better neonatal management not only improves survival, but also long-term pulmonary outcome.

Fig 1. The recruitment of subjects in two cohorts of premature (EP) and matched term-born subjects, one cohort born in 1991–92 and examined in 2001–2002, and one cohort born in 1999–2000 and examined in 2010–2012.

Fig 2. Z-FEV₁ in 11 year old term and preterm-born (EP) subjects born in 1991–92 and 1999–2000, EP-born split by the presence of BPD.

Fig 3. Z-FEF_25–75 in 11 year old term and preterm-born (EP) subjects born in 1991–92 and 1999–2000, EP-born split by the presence of BPD.