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Pros & Cons of Banking Cord Blood

Originally, bone marrow transplants obtained blood stem cells ("hematopoetic" stem cells) from the bone marrow of a matched donor. The USA National Marrow Donor Program (NMDP) maintains a public registry of adults who are willing to consider bone marrow donation, and similar registries exist in other countries. Despite these registries, about 50% of all patients needing a transplant cannot find a matching bone marrow donor.

Umbilical cord blood contains blood stem cells that are even more primitive than the blood stem cells found in bone marrow. They can also be transplanted to regenerate a patient's immune system. The web site of the National Marrow Donor Program is an excellent source of unbiased information about cord blood; just go to the NMDP home page and run a search on the key words "cord blood".

Do not confuse blood, or "hematopoetic", stem cells with "pluripotent" stem cells that come from embryos.  Medical research has found it is possible to use the fundamental, or pluripotent, stem cells from discarded human embryos to grow all manner of human tissues. Obviously, there are serious ethical issues in such research. The NIH website provides a primer on stem cell types. Pluripotent stem cells are not the topic of discussion here. We are only discussing blood stem cells, which can be removed from the umbilical cord without harm to mother or baby, and which can grow a complete immune system of blood cells.
As of late 2000, medical researchers are finding that small numbers of pluripotent stem cells can be harvested from bone marrow, cord blood, and placentas. It even seems that, under some circumstances, "blood" stem cells can be coaxed to grow into other types of tissue. See the page Research on Cord Blood.

The advantages of transplanting with cord blood instead of bone marrow:

  • Harvesting umbilical cord blood poses no risk to mother or child, whereas a bone marrow donor must undergo anesthesia and is exposed to the risk of infection.
  • Umbilical cord blood can be stored in cryogenic freezers, ready for use as soon as it is needed, whereas the process of contacting and testing bone marrow donors listed in a registry takes weeks to months.
  • Because the stem cells in cord blood are more primitive than those in bone marrow, they carry much lower incidence of graft versus host disease (GVHD). Thus, cord blood transplants do not require a "perfect match" between the donor and the patient. 

The disadvantages of transplanting with cord blood instead of bone marrow:

  • Because the stem cells in cord blood are more primitive than those in marrow, the engraftment process takes longer with cord blood, leaving the patient vulnerable to a fatal infection for a longer period of time.
  • A typical cord blood harvest only contains enough stem cells to transplant a large child or small adult (weighing approx. 100 pounds).  Researchers are exploring methods of transplanting adults with cord blood, either by growing the cells in a lab prior to transplant, or by transplanting more than one cord blood unit at a time.  More information about these trials is available on the Research page.

If cord blood is so great, why doesn't everybody bank it?

Because it costs money. Whereas a bone marrow registry is just a data base of potential donors, a cord blood registry consists of freezers full of frozen blood and staff to maintain them. In an ideal world, all babies would have their cord blood harvested at birth (with parental permission) and stored in public registries, much like public blood banks. In practice, only a limited number of institutions have the funding to maintain public banks which take donations for free. A separate web page explains the types of cord blood banks, and another tells you how to find a public bank  to accept your donation.

For most parents, cord blood donation is not an option because the number of locations served by registries is very limited. You have to decide if you feel strongly enough about saving your child's stem cells to pay for private storage.

Will banking my baby's umbilical cord blood provide this child with life-long "medical insurance"?

The probability that the average child will require a transplant of her own stem cells before age 20 has been estimated as 4 in 10,000 (.04%). Reference: Dr. F. Leonard Johnson, Oct1998; Blood & Marrow Transplant Newsletter, issue #43, Oct. 98, vol.9 no.3; originally published: FL Johnson, 1997; J Ped Hem Onc 19(3): 183-186

However, over the course of a lifetime up to age 70, the probability that a person will require a transplant of her own stem cells is 1 in 400 (0.25%). Reference: J.J. Nietfeld and F. Verter 2Oct2004 presentation at Tufts U. Medicine ICBS conference; or PowerPoint slides (808 KB) Several medical and ethical societies have issued opinions against cord blood banking:
However, all of these negative opinions are based purely on pediatric transplant usage, and ignore the possible use of cord blood for adult transplants or regenerative stem cell medicine. Arguments in favor of private banking:
  • One is that, as today's children grow up and some of them develop cancer as adults, autologous (self) cord blood transplants will become more common. The reason is that pediatric cancers and adult cancers are completely different diseases at the cellular level (to learn more about cancer look up the National Cancer Institute). While pediatric cancer patients rarely receive autologous transplants, among adult cancer patients the autologous transplants are more common than transplants from donors.
  • Secondly, recent news reports constantly announce new medical advances using stem cells. Future applications will probably include tissue repair to various organs of the body.
  • Another factor families should consider is whether the odds given for the "average baby" apply to you. Some families do have a higher predisposition to cancer and immune disorders.
  • Finally, if your family, especially your children, are of mixed ethnic background, it may be impossible to find an adult bone marrow donor who is a perfect match. In that event, cord blood from even a partially matched sibling would be invaluable.
Table 1. Cross Race Probabilities for HLA matching

This table displays the mean probability that patients of the indicated race will find a 6/6 HLA-A,B,DR match from amongst a registry of 500,000 donors composed entirely of the indicated race. Reference: copied from the article, "Impact of racial genetic polymorphism upon the probability of finding an HLA-matched donor", by PG Beatty, M Mori, & E Milford, Transplantation 1995; 60(8):778-83

Donor / Patient Caucasian African-
American
Asian-
American 
Hispanic  Native American
Caucasian  .77  .52  .43  .68  .70
Afr.-American  .18  .61  .08  .26  .20
Asian-American  .29  .15  .78  .30  .32
Hispanic  .54  .42  .35  .69  .57
Native American  .61  .49  .53  .71  .76

Table 2. Composition of the NMDP registry as of 31 Dec 2002

 Donor Race  Percentage
 Caucasian  52.4%
 African-American  8.0 %
 Asian/Pacific Islander  6.5 %
 Hispanic  8.5 %
 Native American  1.2 %
 Multi-Racial  2.2 %
 Unknown  21.1 %

Table 3. Likelihood of finding a matching donor in the NMDP registry as of 7/31/2003

Patient Race   Percentage
Caucasian  88 %
African-American  58 %
Asian/Pacific Islander  75 %
Multi-Racial  79 %
Unknown  83 %
 

Limitations to banked cord blood as life-long "medical insurance":

  1. Diseases which require transplantation of blood stem cells are still rare, although the list of diseases amenable to such treatment is steadily growing. They are very rare among children and become more common in adults.
  2. The banked cord blood only provides insurance for so long as the frozen cells are still viable. So far, research has confirmed the long-term viability of cord blood for up to 15 years, but the existing literature on cryogenic storage of living cells indicates that storage for decades is feasible.
  3. The banked cord blood only provides insurance providing there are enough stem cells in the sample for a successful transplant, even after your new baby grows up to become a much larger adult. Again, on-going research is exploring several methods to transplant large adults with banked cord blood.
  4. Even among adults, where autologous transplants with one's own stem cells are more common, there are alternate sources of stem cells in the patient's bone marrow or circulating blood.
  5. Many regenerative therapies are being developed which use the patient's own stem cells. One of the most common and promising is the use of stem cells for heart repair. Adult patients who have banked cord blood would have a ready source of stem cells for regenerative medicine. But again, they also have a rich source of stem cells in their bone marrow.
When parents bank the cord blood from a new baby, in the near term they are most likely providing medical insurance for that child's siblings, and only in the long term when the donor grows up will they have value for self-use.

How much cord blood is needed for a transplant?

The crucial thing is not the volume of the blood sample, but the number of stem cells it contains. These are measured with a test "CD34+" that picks out all mononuclear cells.

The "optimal (transplant) dose is about 20 million nucleated cells per kilogram of body weight" (one kilogram equals 2.2 pounds).

The number of stem cells becomes crucial if cord blood is used for adult patients: "patients who received no more than 10 million nucleated cells per kilogram had a 75 percent probability of death, whereas recipients of at least 30 million nucleated cells per kilogram had a 30 percent probability of death." Reference: Editorial by Gluckman, E. NEJM 2001;344:1860

In a study of 542 families collecting cord blood at several hundred different hospitals, the mean cord blood volume and nucleated cell count were 103.1 mL (including anticoagulant) and 890 million, respectively. Reference: W Reed, et al, Blood 2003; 101(1):351

Thus, on average, a cord blood sample contains 8.6 million nucleated cells per millileter, and a successful transplant requires harvesting 1 millileter of cord blood per pound of patient weight (1 ml and 1 cc are the same amount).
.

Are the potential uses of cord blood likely to increase?

YES! YES! YES! Since the year 2000 there have been dramatic medical advances in the arena of stem cell research, and more are announced every month. See the latest press releases under "News Reports". Highlights:
  • Transplant science is constantly improving.
  • Several companies are bringing to market methods of "expanding" the stem cell population in the laboratory, and these methods are starting to be applied in clinical trials.
  • The evolution from pluripotent stem cells down to blood stem cells is poorly understood. The latest news is that, under the right conditions, stem cells in blood can be teased to grow into other types of tissue besides blood.

As a result of these advances, it is not unreasonable to hope that cord blood may eventually be used to treat a wider variety of auto-immune and degenerative diseases than is currently feasible.
next step...

If I banked cord blood from one child, should I bank the next?

YES!

First, you don't know if the tissue type of the next child will match the previous child. Your children's HLA types come in pairs; in each pair, one is from the mother and one is from the father. The odds of siblings being a perfect match are 1 in 4. A cord blood transplant with a 5/6 or 4/6 mis-match of key HLA types carries less graft-vs-host disease than a perfect 6/6 bone marrow transplant. Reference: V Rocha, et al, 2000; NEJM 342:1846

Second, you can't predict which child may someday need a transplant.

Next: Diseases Treated by Blood Stem Cells