Why is a prolapsed umbilical cord considered dangerous?

A prolapsed umbilical cord is considered dangerous primarily because the baby's head can compress the cord, which can lead to a reduction or complete cutoff of blood flow and oxygen supply to the fetus. The umbilical cord plays a critical role in delivering oxygen and nutrients from the placenta to the baby. When the cord protrudes from the vagina before the baby, and especially if the head descends into the birth canal, it can become compressed between the baby's head and the pelvic wall. This compression can cause variable decelerations in fetal heart rate, indicating that the fetus is experiencing stress due to the lack of adequate oxygenation.

Additionally, the other options mention concerns that might arise in specific situations but do not pertain directly to the primary and immediate danger associated with a prolapsed cord. For instance, while a severed cord could potentially have implications for placental attachment, the direct threat lies in the compromised blood flow due to pressure on the cord. Hypoxia in the mother or possible cord wrapping around the baby's neck are significant, but they do not define the acute risk that a prolapsed cord presents during labor. Thus, the most pressing concern remains the risk of oxygen deprivation to the baby caused by cord compression.