Why does a baby have a ductus arteriosus?
Before birth, the fetus receives needed oxygen from the mother and the placenta. Since the fetus does not need to use his or her lungs, very little blood needs to go to them to help them grow. The ductus arteriosus allows most of the blood instead to bypass the lungs and go to the rest of the body. At birth, the baby’s lungs take over and his or her body stops producing the chemicals that have kept the ductus arteriosus open. Under normal circumstances, the ductus arteriosus gradually narrows and eventually closes in the first few hours to days after birth. If it doesn’t close, the baby has the defect known as patent (open) ductus arteriosus. This defect occurs especially in premature babies who have had respiratory distress syndrome (difficult breathing) due to immature lungs. The cause of PDA is unknown. However, the condition is more common in premature babies as well as those born to mothers who had German measles (rubella) while they were pregnant. What happens when the blood vess