Ovum Cryopreservation: Reality or Hype?
March / April 2005
Whether to preserve a female cancer patient’s eggs
until cancer treatment is completed or to allow a woman to
prolong her fertility while postponing childbearing, the
cryopreservation of oocytes or ovarian tissue, is an important
area of research for reproductive endocrinologists. Cryopreservation
is a precise method used to preserve embryos, eggs, ovarian
tissue and sperm by cooling and storing them at a low temperature
and then thawing them for future use.
Today, cryo-egg clinics are becoming more common and many
women and couples are hoping to successfully freeze their
eggs and defer pregnancy. “The reality is that in human
studies, millions and millions of eggs have been cryopreserved
with just a handful of babies born. So the efficiency of
this system — the starting number of eggs to number
of babies born — is rather discouraging,” says Christos
Coutifaris, MD, PhD, director of the Penn Center for
Reproductive Medicine and Surgery and professor of obstetrics
and gynecology
at the University of Pennsylvania Health System. “This
is in sharp contrast to the relatively highly successful
freezing and thawing of embryos (not eggs).”
Although to date no babies have been born utilizing preserved
ovarian tissue, animal studies suggest that this method holds
more promise than the cryopreservation of single oocytes.
In Europe, a cancer patient had healthy ovarian tissue cryopreserved
and then transplanted back into an ovary where ovulation
later occurred. Although not conclusive, experts agree that
the ovary with the transplanted ovarian tissue produced the
ovulation.
“Normal egg maturation depends on the three-dimensional
structure of the ovary and the different interactions between
the egg and surrounding ovarian cells. That’s why cryopreservation
of ovarian tissue is more appropriate than cryopreservation
of eggs,” adds Dr. Coutifaris.
A September 2004 practice bulletin from the American Society
for Reproductive Medicine concluded that the cryopreservation
of both eggs and ovarian tissue for cancer patients holds
great promise, but at this time should remain an investigational
procedure with strict oversight and be provided at no charge
to patients. The report further concluded that neither oocyte
nor ovarian tissue preservation should be offered or marketed
as a means to defer reproductive aging.
“Women and couples seeking ovum cryopreservation are
extremely vulnerable and are often willing to invest an exorbitant
amount of money in this technology even though it has a very
low chance of success,” adds Dr. Coutifaris. “It
is important for primary care physicians to know the facts
about fertility and age, provide their patients with realistic
expectations, and refer their patients to a board-certified
fertility specialist if they are over age 30 and are having
trouble conceiving.”
Women are born with approximately one million follicles
in their ovaries and by puberty just 300,000 remain. This
number continues to decline until menopause when almost no
follicles are left in the ovaries. “For women with
a diminished ovarian reserve or who are experiencing early
menopause, or who have undergone cancer treatment, using
eggs donated by a young, healthy woman is the best chance
for conception and a live-birth,” says Dr. Coutifaris.
Recent national data showed an approximate 50 percent live-birth
rate for patients over age 38 who used fresh donor eggs.
“The use of donor eggs allows a dramatic increase
in the chance a woman will conceive because the age of the
donor determines the success of the cycle, not the age of
the recipient. Therefore, if a 41-year-old woman selects
a 24-year-old donor, her pregnancy success rate will be that
of a 24-year-old woman as long as the recipient has a normal
uterus,” explains Dr. Coutifaris.
Penn is one of only eight centers in the nation funded by
the National Institutes of Health (NIH) to perform clinical
infertility research and the only center funded by the NIH
for laboratory research specifically related to infertility.
When Should Your Patient See a Fertility Specialist? |
- If the woman is under age
35 and has not conceived after a year of trying to
get pregnant.
- If the woman is over age 35
and has been unable to conceive after six months
of trying.
- If the woman has lost two or
more pregnancies to miscarriage.
- If other
infertility treatments have not been successful.
- If
the patient does not have regular menstrual cycles,
or has had a prior gynecological problem (e.g. endometriosis,
tubal pregnancy, pelvic surgery or infections), she
should seek assistance sooner.
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