The ductus arteriosus is an important blood vessel that connects the main pulmonary artery and the aorta. Normally, the ductus arteriosus exists for 2-6 days after birth. If the ductus does not close after this time, it is called a persistent ductus arteriosus. Persistent ductus arteriosus in premature infants (Persistent ductus arteriosus) occurs when the ductus arteriosus does not close completely after birth.