Benefits

Umbilical cord blood is more available than bone marrow: This is true in part because bone marrow transplants require a more precise tissue match than do umbilical cord blood transplants.

Every newborn is a potential donor: As a result, patients' needs and not donors' schedules dictate the timing of transplant.

Better availability means cord blood transplants can be performed more quickly than bone marrow transplants once a virulent cancer is diagnosed: By contrast, bone marrow transplant patients may wait months for a suitable donor. In 25 percent of the cases, a bone marrow donor is not available when the patient needs the transplant.

Even when a suitable bone marrow match is found, the donor may not be in a position to undergo the surgery that marrow-extraction requires.

With an umbilical cord blood transplant, banked blood is nearly always available.

Risks

As with any medical procedure, there are risks, as well.

The risk posed by umbilical cord blood is that its stem cells do take longer than the stem cells of bone marrow to begin working: Particularly for adults with small umbilical cord blood grafts, it may be twice as long depending on the cell dose.

This time lag is critical: It means the patient is vulnerable to infection because the blood has not yet rebuilt its infection-fighting system.

To overcome the time lag, doctors try to do with drugs and stem cell expansion what the body can do naturally.