Storage of blood from the umbilical cord. Blood in the umbilical cord is rich in blood cells that are able to replenish the bone marrow and are able to transform into cells of different organs. Freezing cord blood cells immediately after delivery preserves these cells should the baby need a bone marrow transplant in the future. It is not now clear that this should be done or how useful these cord blood specimens will be in the future. The potential usefulness of cord blood is the subject of much ongoing research.