In fetal circulation, blood flow normally bypasses the lungs, because oxygen and nutrients are received from the placenta and the umbilical cord. After birth, when the infant begins to breathe, two passageways in the circulatory structure of the heart called the foramen ovale and the ductus arteriosus close in order to deliver fully oxygenated blood to the body. If the ducts do not close at birth, some of the blood in the left side of the heart will go to the lungs instead of to the general circulation. The disorder can occur in both premature and full-term infants. Usually symptoms are mild, but they become more pronounced if not corrected by the age of 2.
Risk factors are prematurity and respiratory distress syndrome .
The incidence is 60 out of 100,000 infants. The infant may have a bounding pulse . In full-term infants, surgical ligation of the patent ductus is indicated if heart failure develops. If the infant is asymptomatic , the surgery is postponed until 6 months to 3 years of age, unless problems develop. Parents with an infant whose ductus has recently closed are encouraged not to fly as the decrease in oxygen may cause the ductus to reopen.