When does the ductus venosus typically close?

The ductus venosus is a crucial fetal blood vessel that connects the umbilical vein to the inferior vena cava, allowing oxygen-rich blood from the placenta to bypass the liver and flow directly into the heart. This bypass is essential during fetal development because the liver is not fully functional before birth.

Typically, the ductus venosus closes functionally shortly after birth. This closure occurs as immediate changes in blood flow dynamics take place when the newborn begins to breathe air for the first time, which leads to a decrease in pressure in the right atrium of the heart. This change promotes the closure of this vascular shunt, which usually happens within the first few minutes to hours post-delivery.

Anatomically, the ductus venosus may take some additional time to fully obliterate and become a fibrous structure known as the ligamentum venosum, which typically occurs within the first week of life. However, the immediate functional closure following birth is what is primarily referred to as the correct answer in this case.

In contrast, the other choices suggest either a later timing for closure or imply a permanence that does not reflect the physiological process observed in most newborns. Thus, the timing of closure signifies the transition from fetal to