Pulmonary hemorrhage and its association with bronchopulmonary dysplasia in very low birth weight infants with gestational age < 32 weeks

Pulmonary hemorrhage is a critical condition that causes acute lung injury in very low birth weight infants (VLBWIs), a population at high risk for developing bronchopulmonary dysplasia (BPD). This study investigates the association between pulmonary hemorrhage and the development of BPD. This retrospective cohort study included 963 VLBWIs (gestational age < 32 weeks, birthweight < 1500 g) admitted to a Level IV neonatal intensive care unit between January 2018 and January 2025. Participants were divided into a pulmonary hemorrhage group (n = 137) and a non-pulmonary hemorrhage group (n = 826). The primary analysis employed a competing-risk model (Fine-Gray subdistribution hazard model) to estimate the association between pulmonary hemorrhage and BPD, treating death as a competing event. Secondary analyses included binary logistic regression for a composite outcome (BPD or death) and for BPD risk among survivors to 36 weeks postmenstrual age (PMA). Confounders were selected using directed acyclic graphs (DAG) and least absolute shrinkage and selection operator regression. In the competing-risk model, pulmonary hemorrhage was associated with a lower cumulative incidence of BPD (hazard ratio (HR) 0.57; 95% confidence interval (CI) 0.39–0.81; P = 0.002) because of the high early mortality rate in the pulmonary hemorrhage group. However, pulmonary hemorrhage was significantly associated with a higher risk of the composite outcome of BPD or death (adjusted odds ratio (aOR) 11.15; 95% CI 5.87–21.16; P < 0.001). Among infants who survived to 36 weeks PMA, pulmonary hemorrhage was an independent risk factor for both BPD (aOR 3.43; 95% CI 1.84–6.41; P < 0.001) and moderate-to-severe BPD (aOR 4.37; 95% CI 1.55–12.30; P < 0.001). While pulmonary hemorrhage is associated with high early mortality, it significantly increases the risk of BPD and moderate-to-severe BPD among survivors. Clinical management should focus on the long-term respiratory morbidity of infants surviving a pulmonary hemorrhage event.