Methods: Participants: Extremely preterm infants (\<29 weeks gestational age) with an echocardiography confirmed PDA who will be treated according to attending team Interventions: 1. Standard dose ibuprofen \[10-5-5 regimen, i.e., 10mg/kg followed by 2 doses of 5mg/kg at 24h intervals\] 2. Adjustable dose ibuprofen \[10-5-5 regimen if treated within the first week. Higher doses of ibuprofen up to a 20-10-10 regimen if treated after the postnatal age cut-off for lower dose as per the local center policy\] 3. Intravenous indomethacin \[0.1-0.3mg/kg every 12-24h for a total of 3 doses\]. 4. Acetaminophen \[Oral/intravenous\] (15mg/kg every 6h) for 3-7 days Outcomes: Primary: Failure of primary pharmacotherapy (Need for further medical and/or surgical/interventional treatment following an initial course of pharmacotherapy). Secondary: (a) Receipt of 2nd course of pharmacotherapy; (b) Surgical/interventional PDA closure; (c) CLD (d) NEC (stage 2 or greater) (e) Severe IVH (Grade III-IV) (f) Definite sepsis (g) Stage 1 or greater AKI; (h) Post-treatment serum bilirubin; (i) Phototherapy duration; (j) All-cause mortality during hospital stay.