After you note a murmur in a newborn, the pediatric cardiology consultant diagnoses a patent ductus arteriosus. Why is this a cause for concern?

Patent ductus arteriosus (PDA) is an extra blood vessel found in babies before birth and just after birth.

Explanation:

The ductus arteriosus is a normal blood vessel that connects two major arteries — the aorta and the pulmonary artery — that carry blood away from the heart.

The lungs are not used while a fetus is in the womb because the baby gets oxygen directly from the mother's placenta. The ductus arteriosus carries blood away from the lungs and sends it directly to the body. When a newborn breathes and begins to use the lungs, the ductus is no longer needed and usually closes by itself during the first 2 days after birth.

If the ductus doesn't close, the result is a patent (meaning "open") ductus arteriosus. The PDA lets oxygen-rich blood (blood high in oxygen) from the aorta mix with oxygen-poor blood (blood low in oxygen) in the pulmonary artery. As a result, too much blood flows into the lungs, which puts a strain on the heart and increases blood pressure in the pulmonary arteries.