BACKGROUND: Extremely preterm infants with evolving bronchopulmonary dysplasia (BPD) are at risk for development of BPD-associated pulmonary hypertension (BPD-PH). The presence and duration of a patent ductus arteriosus (PDA) shunt may be a modifiable risk factor for BPD-PH development. METHODS: Retrospective case-control study among preterm infants 22w 0d to 28w 6d who remained on respiratory support on postnatal day 28 at the University of Alabama at Birmingham from 2017-2020. Infants who were diagnosed with pulmonary hypertension (cases) by echocardiography were compared to infants without pulmonary hypertension (controls). Data from echocardiograms performed during the hospitalization after postnatal day 28 were included. Generalized linear models adjusted for covariates that differed significantly between groups. A probit analysis related the duration of ductal patency to the development of BPD-PH. RESULTS: 138 infants developed BPD alone and 82 infants developed BPD-PH. Following adjustment for differing covariates between groups, both PDA (aOR 4.29; 95% CI 1.89 - 9.77) and moderate to large PDA (aOR 4.15; 95% CI 1.78 - 9.64) remained significantly related to BPD-PH at discharge. By probit analysis each additional month of PDA and hemodynamically significant PDA exposure was associated with an increased probability for the composite outcome of BPD-PH at discharge or death with coefficients of 0.40 (p<0.001) and 0.45 (p<0.001) respectively. CONCLUSIONS: In extremely preterm infants on respiratory support on postnatal day 28, both presence of and longer duration of ductus arteriosus patency was associated with the development of BPD-PH.