Inclusion Criteria:  Preterm infants less than 26 completed weeks (i.e., up to and including 25 weeks and 6 days) of gestation  Exclusion Criteria:  no PDA on initial screening echocardiography congenital heart disease (excluding patent foramen ovale, atrial septal defect or ventricular septal defect with a defect size less than 2mm) other major congenital anomaly decision to withhold/withdraw care