What is the expected mean closure time of the ductus arteriosus in full-term neonates?

The expected mean closure time of the ductus arteriosus in full-term neonates is typically around 1-2 days after birth. The ductus arteriosus is a blood vessel that connects the pulmonary artery to the aorta, allowing blood to bypass the non-functioning lungs in utero. After birth, as the neonate begins to breathe air and the lungs become functional, there is a decrease in circulating levels of prostaglandins, which are responsible for keeping the ductus arteriosus open.

Within the first 24-48 hours after birth, the ductus usually begins to constrict and closes functionally. Complete anatomical closure can take a bit longer but is expected to occur within the first week of life. Thus, the timeframe of 1-2 days aligns well with the physiological changes that take place following birth in full-term infants, making this the correct answer.

Other options suggest either an immediate or extended closure time that does not accurately reflect the normal physiological process in full-term neonates.