Risk factors for pulmonary artery hypertension in preterm infants with moderate or severe bronchopulmonary dysplasia

Background: Despite the potential importance of pulmonary artery hypertension (PAH) in preterm infants with bronchopulmonary dysplasia (BPD), little is known about the risk factors for PAH. Objectives: To investigate the risk factors for PAH in preterm infants with BPD. Methods: Infants diagnosed with BPD were assigned to the PAH group or non-PAH group except for infants with mild BPD who had no PAH. PAH was diagnosed on the basis of echocardiograms demonstrating elevated right ventricle pressure beyond the postnatal age of 2 months. Logistic regression analysis was done for the multivariate assessment of the risk factors for PAH in preterm infants with moderate or severe BPD. Results: A total of 98 infants among 145 infants with BPD were divided into a PAH group (n = 25) or non-PAH group (n = 73), while the remaining 47 infants had mild BPD with no PAH. Among the study patients, survival rate of the PAH group was significantly lower than that of the non-PAH group. Infants with PAH had more severe cases of BPD and underwent longer durations of oxygen therapy, conventional or high-frequency ventilation, and hospitalization compared to those without PAH. Low 5-min Apgar scores (≤6; relative risk (RR) 6.2; 95% confidence interval (CI) 1.4-28.0; p = 0.017) and oligohydramnios (RR 7.7; 95% CI 2.0-29.6; p = 0.030) were found to be significant risk factors for PAH according to multivariate analysis. Conclusions: The present study shows that oligohydramnios is a specific risk factor for PAH in preterm infants with moderate or severe BPD.