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 among those used in clinical practice: If the mother is far from delivery, funic reduction (manually placing the cord back into the uterine cavity) has been attempted, with successful cases reported. The primary concern with umbilical cord prolapse is inadequate blood supply, and thus oxygen, to the fetus if the cord becomes compressed. The cord can become compressed either due to mechanical pressure (usually from the presenting fetal part) or from sudden contraction of the vessels due to decreased temperatures in the vagina in comparison to the uterus. This can lead to death of the fetus or other complications. Historically,