OBJECTIVE: To identify risk factors for late pulmonary artery hypertension (PH) at 36 weeks' postmenstrual age (PMA) in infants born before 28 weeks' gestation. DESIGN/METHODS: A retrospective cohort study included infants born <
28 weeks' gestation who underwent PH screening echocardiography at 36 weeks' PMA. We compared characteristics between infants with and without late PH to determine associations. RESULTS: Of 99 infants, 20 (20%) developed late PH. The FiO2% requirement at 4 weeks of age, home oxygen use, and procedural patent ductus arteriosus closure were associated with late PH. Bronchopulmonary dysplasia (BPD) severity was linearly associated with late PH, with each 1-point increase in BPD severity corresponding to a 3.5-fold increased odds of late PH diagnosis. CONCLUSION(S): One in five extremely premature infants developed late PH. Markers of respiratory disease severity, including the BPD grade, were associated with the development of late PH.