Part of the fetal circulation. It directly connects the left pulmonary artery to the aorta, thereby bypassing circulation of the non-ventilated lungs and resulting in re-circulation of arterial blood through the lungs (see figure below). If it persists after delivery in live births of 2500 grams or more, then surgery may be required to close the lumen (inner channel or connecting blood vessel) in the ductus ateriosus.
