Pulmonary function in former preterm infants may be compromised during childhood.

To assess pulmonary function in very-low-birth-weight preterm infants at 6–12 months of corrected age and analyze the factors associated with abnormal pulmonary function.

Cross-sectional study with preterm infants at 6–12 months of corrected age with birth weight <1500 g. Children with malformations or affected by neuromuscular and respiratory diseases were excluded. Forced expiratory flows were assessed using the chest compression technique, and volumes were measured by total body plethysmography. Pulmonary function parameters in preterm infants were compared to a control group of same-aged children born at term.

We studied 51 preterm and 37 infants born at term. Preterm infants had: gestational age at birth (30.0 ± 2.5 weeks), birth weight (1179 ± 247 g), 27.5% had bronchopulmonary dysplasia, and 45% received mechanical ventilation. Preterm infants had lower median z-scores in comparison to term infants for the following parameters (p < 0.05): FVC (−0.3 vs. 0.7), FEV_0.5 (−0.5 vs. 0.9), FEV_0.5/FVC (−0.6 vs. −0.5), FEF₅₀ (−0.4 vs. 0.9), FEF₇₅ (−0.3 vs. 0.8), FEF₈₅ (−0.1 vs. 0.6) and FEF_25-75 (−0.5 vs. 1.1). No term child had abnormal lung function, compared to 39.2% of preterm infants (p = 0.001). Factors associated with abnormal pulmonary function were lower gestational age at birth, small for gestational age, need for mechanical ventilation and presence of recurrent wheezing.

Preterms had a high prevalence of abnormal pulmonary function and lower pulmonary function in comparison to term infants. Prematurity, intrauterine growth restriction, respiratory support and recurrent wheezing were associated with abnormal pulmonary function.