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
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
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
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
Will banking my baby's umbilical cord blood provide this child with life-long
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%).
Nietfeld and F. Verter
2Oct2004 presentation at Tufts U. Medicine
ICBS conference; or PowerPoint
(808 KB) Several medical and ethical societies have issued
opinions against cord blood banking:
of these negative opinions are based purely on pediatric
usage, and ignore the possible use of cord blood for adult
transplants or regenerative stem cell medicine. Arguments in favor of private
- 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
Table 2. Composition of the NMDP registry
as of 31 Dec 2002
Table 3. Likelihood of finding a matching donor in the NMDP registry
as of 7/31/2003
| Donor Race
|| 8.0 %
| Asian/Pacific Islander
|| 6.5 %
|| 8.5 %
| Native American
|| 1.2 %
|| 2.2 %
|| 21.1 %
|| 88 %
|| 58 %
|| 75 %
|| 79 %
|| 83 %
Limitations to banked cord blood as life-long "medical insurance":
- 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
- 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.
- 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
- 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.
- 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
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
- 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
As a result of these advances, it is not unreasonable to hope that cord blood
be used to treat a wider variety of auto-immune and
degenerative diseases than is currently feasible.
If I banked cord blood from one child, should I bank the next?
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