Umbilical cord from and contains remnants of the yolk sac and allantois. It forms by the fifth week of development, replacing the yolk sac as the source of nutrients for the embryo. The cord is not directly connected to the mother's circulatory system, but instead joins the placenta, which transfers materials to and from the maternal blood without allowing direct mixing. The length of the umbilical cord is approximately equal to the crown-rump length of the fetus throughout pregnancy. The umbilical cord in a full term neonate is usually about 50 centimeters (20 in) long and about 2 centimeters (0.75 in) in
Umbilical cord prolapse should be suspected if there is a sudden decrease in the babies heart rate during labor. Seeing or feeling the cord confirms the diagnosis. Management focuses on quick delivery, usually by cesarean section. Filling the bladder or pushing up the baby by hand is recommended until this can take place. The knee-chest position, or if this is not possible Trendelenburg position may be used. With appropriate management, the majority of cases have good outcomes. Umbilical cord prolapse occurs in about 1 in 500 pregnancies. The risk of death of the baby is about 10%. Much of this risk is due