Chief investigator- Multi-centre, masked, randomised placebo-controlled parallel group trial to determine short and long term health and economic outcomes of the treatment of a large Patent Ductus Arteriosus (PDA) in extremely pre-term babies with ibuprofen within 72 hours of birth. Primary Endpoints: Death or BPD at 36 weeks PMA 730 pre-term babies : • Born at 23+0 to 28+6 weeks of gestation • Confirmed by echocardiography to have a large PDA 25 UK tertiary (level 3) neonatal units.