Cord blood (resi­du­al pla­cen­tal blood) is the blood remai­ning in the umbi­li­cal cord and the pla­cen­ta after a child is born and the umbi­li­cal cord is cut. Umbi­li­cal cord blood is rich in stem cells, as during the last three mon­ths of pregnan­cy a “migra­ti­on” takes place in the child’s blood-forming sys­tem. Blood pro­duc­tion initi­al­ly occurs in the liver and spleen of a fetus, but then migra­tes into the bone mar­row. This migra­ti­on takes place in the child’s bloo­d­stream. For this rea­son, an extre­me­ly lar­ge num­ber of stem cells are found in the child’s blood at the time of birth and the­re­fo­re also in the blood remai­ning in the umbi­li­cal cord and placenta.