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
Jewish women in the Holocaust and emotionally. Once labor was over and the baby was born, the women vulnerable to being killed along with their baby. One memoir describes some of the sadistic acts, which were performed among those who were pregnant: "SS men and women amuse themselves by beating pregnant women with clubs and whips, [being] torn by dogs, dragged around by the hair and kicked in the stomach with heavy German boots. Then when [the pregnant Jewish women] collapsed, they were thrown into the crematory-alive." Several Jewish women who wrote their own memoirs reflecting on the Holocaust reported there being a double jeopardy