After a baby is born and the umbilical cord is cut, some blood remains in the blood vessels of the placenta and the portion of the umbilical cord that remains attached to it. After the baby is born, he or she will no longer need this extra blood. This blood is the placental blood or umbilical cord blood.

      Cord blood is collected because it contains stem cells, including hematopoietic cells, which can be used to treat hematopoietic and genetic disorders.
Cord blood contains all the normal elements of blood - red blood cells, white blood cells, platelets and plasma. But it is also rich in hematopoietic (blood-forming) stem cells, similar to those found in bone marrow. This is why cord blood can be used for transplantation as an alternative to bone marrow.

      Cord blood is being used increasingly on an experimental basis as a source of stem cells, as an alternative to bone marrow. Cord Blood transplants have also been performed for patients with genetic or metabolic diseases.  More than 80 different diseases have been treated to date with unrelated cord blood transplants.

      Scientists are investigating the possibility that stem cells in cord blood may be able to replace cells of other tissues such as nerve or heart cells. Whether cord blood can be used to treat other kinds of diseases will be learned from this research. Although the cord blood does contain stem cells, there are generally not enough stem cells in one unit of cord blood to treat an adult patient. The placenta is a much better source of stem cells since it contains up to ten times more stem cells than cord blood.