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.