Perinatal risk factors and lung function at 8 years of age in extremely preterm infants: Insights from a new Japanese bronchopulmonary dysplasia classification.

BACKGROUND

Advances in neonatal care have considerably improved the survival rates of extremely preterm infants. However, long-term pulmonary sequelae remain a major concern. A revised classification of bronchopulmonary dysplasia (BPD) in Japan highlights histological chorioamnionitis, small for gestational age (SGA), and a bubbly/cystic appearance on chest X-ray (bubbly/cystic CXR) as key risk factors. This study aimed to evaluate the effect of extremely preterm birth on lung function at school age.

METHODS

This retrospective study included 283 extremely preterm infants (born at <28 weeks of gestation) admitted to our institution between 1994 and 2013. Perinatal data and spirometry results obtained at 8 years of age were analyzed. Logistic regression analysis was performed to assess the association of histological chorioamnionitis, SGA, and bubbly/cystic CXR with obstructive (FEV1 [forced expiratory volume in 1 s]/FVC [forced vital capacity] < LLN [lower limit of normal]), restrictive (FEV1/FVC ≥ LLN and FVC < LLN), and mixed (FEV1/FVC < LLN and FVC < LLN) patterns, with adjustments for gestational age, sex, and birth year.

RESULTS

Extremely preterm infants exhibited lower z-scores for FEV1/FVC, FEV1, and FVC than the predicted values based on age, height, and sex. Bubbly/cystic CXR findings was associated with an increased risk of obstructive (adjusted odds ratio [aOR], 2.30; 95 % confidence interval [CI], 1.12-4.72) and mixed patterns (aOR, 3.51; 95 % CI, 1.19-10.4). SGA was a risk factor for a restrictive pattern (aOR, 2.81; 95 % CI, 1.37-5.74).

CONCLUSION

Bubbly/cystic CXR findings and SGA status, key components of the revised Japanese BPD classification, were significantly associated with long-term pulmonary function abnormalities in extremely preterm infants, characterized predominantly by obstructive/mixed and restrictive patterns, respectively. These findings highlight the importance of targeted strategies to address specific perinatal risk factors and improve long-term pulmonary outcomes in this high-risk population.