Final answer:
The ductus arteriosus typically closes within a day or two of birth in newborns.
Step-by-step explanation:
The ductus arteriosus is a short, muscular vessel that connects the pulmonary trunk to the aorta. It shunts most of the blood pumped from the right ventricle into the aorta, bypassing the fetal lungs. However, after birth, as the newborn takes the first breath, there is a decrease in resistance in the lungs and the blood circulation changes. This causes the ductus arteriosus to close, typically within a day or two of birth.