What occurs to the ductus venosus upon clamping of the umbilical cord?

• A. It relaxes and opens
• B. It immediately closes functionally
• C. It constricts gradually over several hours
• D. It remains unaffected by cord clamping

Answer: (B)

Upon clamping of the umbilical cord, the ductus venosus immediately closes functionally. This physiological change is a critical transition as the newborn begins to adapt from fetal to extrauterine life. The ductus venosus is a vascular connection between the umbilical vein and the inferior vena cava, allowing oxygen-rich blood from the placenta to bypass the liver during fetal development.

When the umbilical cord is clamped, this influx of blood ceases, leading to a decrease in blood flow through the ductus venosus. The sudden disruption in blood flow triggers the smooth muscle in the ductus venosus to contract, causing it to close off functionally. This closure is an essential step in redirecting blood flow to the liver and lungs, which become increasingly functional after birth.

Understanding this process emphasizes the significance of the ductus venosus in fetal life and its rapid transition to closure, which is vital for proper neonatal hemodynamics.