What happens to the ductus arteriosus after the baby's first breath?

• A. It becomes the fossa ovalis
• B. It converts to the ligamentum venosum
• C. It remains open and dilates
• D. It constricts and becomes the ligamentum arteriosum

Answer: (D)

After birth, the ductus arteriosus constricts in response to the rise in blood oxygen and the fall in circulating prostaglandins, leading to functional closure. Over time this vessel fibroses and becomes the ligamentum arteriosum, a fibrous remnant that sits between the aorta and the pulmonary artery. This closure redirects blood to the lungs for oxygenation. The fossa ovalis is the remnant of the foramen ovale, and the ligamentum venosum is the remnant of the ductus venosus; if the ductus arteriosus stayed open, it would continue to shunt blood away from the lungs.