Below. The ductus arteriosus (DA) is a normal blood vessel that connects two major arteries — the aorta and the pulmonary artery — that carry blood away from the heart in a developing fetus. The DA diverts blood away from the lungs, sending it directly to the body. The lungs are not used while a fetus is in the amniotic fluid because the baby gets oxygen directly from the mother's placenta. When a newborn breathes and begins to use the lungs, the DA is no longer needed and usually closes during the first 2 days after birth. But when the DA fails to close, a condition called patent (meaning "open") ductus arteriosus (PDA) results, in which oxygen-rich blood from the aorta is allowed to mix with oxygen-poor blood 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. Treatment The three treatment options for PDA are medication, catheter-based procedures, and surgery.