What Is the Function of the Ductus Arteriosus in Unborn Mammals?

The ductus arteriosus shunts blood away from the lungs of fetal mammals because the fetus cannot get oxygen from its own lungs until it is born. The blood vessel connects the pulmonary artery to the aorta, meanwhile getting oxygen from the mother's umbilical cord. When the mammal is born, the ductus arteriosus constricts and becomes part of the aorta as the ligamentum arteriosum.

The ductus arteriosus closes when a substance called bradykinin is released by the body upon the opening of the lungs. When enough oxygenated blood enters the aorta, the wall of the ductus arteriosus constricts permanently. This artery also closes at birth to reduce blood loss from the newborn. Constriction of this duct signifies the newborn's ability to circulate blood on its own.

Most of the blood supplied to the lower part of fetal mammals passes through the ductus arteriosus. After passing through this duct, blood flows to the umbilical arteries and to the placenta. Here, blood waste is removed and new oxygen is delivered.

The most common disorder associated with this blood vessel is patent ductus arteriosus, a congenital heart defect that occurs in 5 to 10 percent of preterm babies. This disorder occurs in one newborn in every 2,000 live births overall. Patent ductus arteriosus happens due to genetics or some kind of infection during pregnancy.