The most common heart condition affecting premature babies is called a patent ductus arteriosus. Prior to birth, the ductus arteriosus connects the two main arteries leaving the baby's heart-the pulmonary artery, which pumps blood to the lungs, and the aorta, which pumps blood to the rest of the body. The ductus usually closes when the baby is born, separating the two arteries. In premature babies, however, the ductus arteriosus may remain open (patent), causing extra blood to be pumped through the lungs in the first days of life. Fluid can build up in the lungs, and heart failure can develop.

Fortunately, babies can be treated with indomethacin, a medication that causes the ductus arteriosus to close. Greater than 80% of premature babies who have an open ductus arteriosus improve with indomethacin. If it remains open and symptomatic, an operation to close the duct may be required.