The TREOCAPA clinical trial deals with the effective prophylaxis (a measure to prevent a disease) of a persistent ductus arteriosus (PDA) (see next paragraph below), which often occurs in very preterm born children. The trial is conducted in approximately 65 Neonatal Intensive Care Units (NICUs) in 17 European countries. Preterm infants of a gestational age of 23 to 28 weeks are included in the study. INSERM, a biomedical French research institute, is the sponsor of the trial which is led by Nantes University Hospital in France. The TREOCAPA trial is a Proof of Viability study of the Conect4Children (c4c) project, which aims to develop a Pan European Paediatric Clinical Trial Network.