Question: when does closure of the ductus arteriosus occur?
Answer: at birth, birth

In the developing fetus , the ductus arteriosus , also called the ductus Botalli , is a blood vessel connecting the main pulmonary artery to the proximal descending aorta . It allows most of the blood from the right ventricle to bypass the fetus 's fluid - filled non-functioning lungs . Upon closure at birth , it becomes the ligamentum arteriosum . There are two other fetal shunts , the ductus venosus and the foramen ovale .