This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pediatrics
In full-term neonates, the ductus aeriosus closure is due to 
Select and explain. 
A. Cardiac output, B. Prostaglandins, C. Low pressure CO2, D. Low pressure O2
D: Low pressure O2
Answer: D: Low pressure O2 
Explanation: The increasing oxygen saturation and the high aerial po2 causes the muscle of ductus to constrict and eventually closes the ductus aeriosus which eventually becomes ligamentum aeriosum.Anatomical closure of ductus aeriosus occurs within 10 to 25 days.Flow through ductus venosus disappears by the 7th day of postnatal life.