BackgroundProlonged pulmonary hypertension (PH) is highly predictive for pulmonary morbidity and death in infants with congenital diaphragmatic hernia (CDH). ObjectivesTo report the effects and tolerability of subcutaneous treprostinil in newborns with severe CDH and late life-threatening PH. MethodsWe recorded clinical and echocardiography data before and after starting subcutaneous treprostinil, on patients with severe CDH and late PH, refractory to inhaled nitric oxide and oral sildenafil. Results14 patients were treated with treprostinil (gestational age: 39.1±2.0weeks; birth weight: 3200±600g). Prior to treatment, the pre- and post-ductal SpO2 difference (Δ SpO2) was 14±10%. Treprostinil was initiated at a median age of 12days [5–157]. After starting treprostinil, ΔSpO2 decreased to 3% at day 7 (p<0.05), and the mean blood flow velocities in the right pulmonary arteries increased by 110% (p<0.05). 2 of the 14 patients died. At the age of follow up (12months to 3years), the 12 surviving infants were all weaned from respiratory support and discharged home. ConclusionThe subcutaneous treprostinil improves pulmonary hemodynamics and outcomes in infants with CDH and life-threatening PH. We suggest that the treatment should be considered in infants with severe CDH and late PH. Type of studyCase series with no comparison group. Level of evidenceLevel IV.