The ductus arteriosus is a blood vessel in a developing fetus that connects the pulmonary artery to the aorta. This connection allows blood to bypass the lungs, which are not yet functioning, as the fetus receives oxygen from the mother's blood. The ductus arteriosus is crucial for proper fetal circulation. After birth, the ductus arteriosus usually closes within the first few days of life, transforming into a fibrous cord. If it remains open, a condition known as patent ductus arteriosus can occur, which may lead to heart problems and requires medical attention.