RATIONALE: Bedside biomarkers that allow early identification of infants with bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH) are critically important given the higher risk of death in these infants. OBJECTIVE: We hypothesized that infants with BPD-PH have patterns of intermittent hypoxemia that differ from infants with BPD without pulmonary hypertension. METHODS: We conducted a matched case-control study of extremely preterm infants 22w 0d to 28w 6d born between 2018 and 2020 at the University of Alabama at Birmingham. BPD-PH status was determined using echocardiographic data performed after postnatal day 28. Physiologic data were compared between infants with BPD-PH (cases) and BPD alone (controls). Receiver operating characteristic (ROC) analysis estimated the predictive ability of cumulative hypoxemia, desaturation frequency, and duration of intermittent hypoxemic events in the week preceding echocardiography to discriminate between cases and controls. MEASUREMENTS AND MAIN RESULTS: 40 infants with BPD-PH were compared to 40 infants with BPD alone. Infants with and without PH had a similar frequency of IH events, but infants with PH had more prolonged hypoxemic events for desaturations below 80% (7s vs 6s; p=0.03) and 70% (105s vs 58s; p=0.008). Among infants with BPD-PH, infants who died had longer hypoxemic events below 70% (145s vs 72s; p=0.01). Using the duration of hypoxemic events below 70%, the areas under the ROC curves for diagnosis of BPD-PH and death in BPD-PH infants were 0.71 and 0.77, respectively. CONCLUSIONS: Longer duration of intermittent hypoxemic events was associated both with a diagnosis of BPD-PH and with death among infants with BPD-PH.