Ductus arteriosus connects the aorta and the pulmonary artery during the fetal circulation. Functional closure occurs in the first hours of life by contraction of the walls, true anatomic closure occurs at 10th – 20th day after birth by adhesion of the walls and obliteration of the lumen.
In the very premature newborns the closure of the ductus is delayed because of the immaturity of the duct wall.
On the other hand the patent ductus in a full term infant is probably caused by a structural wall abnormity. Through the ductus the blood flows from the aorta to the pulmonary artery (left-to-right shunt). Clinical symptomes and the risk of pulmonary hypertension depend on the width of the ductus.
In immature infants the closure can be affected pharmacologically — indometacin). In the other cases catatherization techniques or surgical ligation of the ductus are performed.