Normally, a blood vessel needed only for fetal blood circulation (called the ductus arteriosus) closes off at birth. During fetal development, this blood vessel is kept open by a naturally occurring substance in the fetus's body called prostaglandin. At birth, fetal production of prostaglandin decreases and the ductus arteriosus closes.

In some premature infants, this blood vessel does not close, which is a condition called a patent (open) ductus arteriosus. These premature infants are given a prostaglandin inhibitor, a medicine to stimulate the closure of this blood vessel.

When an infant has certain other congenital heart defects, a medicine (a form of prostaglandin) is often given by vein to keep the ductus arteriosus open. Keeping this blood vessel open allows the blood to continue circulating until surgery or another procedure can be done to correct the related defect and allow normal blood flow.