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Embryo cryopreservation may be an option for women undergo ovulation induction
with follicle stimulating hormone (FSH) during in vitro
fertilization, IVF,
cycles. FSH stimulates the development of multiple follicles
each of which contains an egg. Once these eggs mature,
they are aspirated using ultrasound guided transvaginal
retrieval. The number of eggs available for use in the
IVF cycle depends upon many patient specific variables.
Once the eggs
are retrieved and separated, each is exposed to
sperm in a culture dish. If the patient needs ICSI,
a sperm will be injected directly into each egg. The
fertilized eggs are then transferred to incubators where
they develop until ready for transfer to the uterus,
usually 3-5 days.
The number of mature embryos available
for transfer varies by patient, as does the number placed
back in the uterus. Since the maximum number of embryos
that will be transferred to the uterus is limited, there
are often excess embryos. Once the embryos are formed, PGD will be performed where indicated.
Cryopreservation (embryo freezing) is the freezing
and thawing of "excess" embryos for use in future IVF
cycles. Embryologists have perfected techniques
for sequentially transferring embryos to different solutions
as they are frozen and thawed. Great care is taken not
to rupture the membrane surrounding the embryo (zona
pellucida).
The major advantages to using cryopreserved
embryos in future IVF cycles is that the female does
not have to undergo ovulation induction, which also
dramatically reduces medication cost. Success rates
are variable depending on patient characteristics, embryo
quality and clinical history. (See
our section on success rates for more information)
Huntington Reproductive Center
is actively involved in research to perfect egg freezing
and thawing technology. The ability to successfully
freeze eggs will assist in reducing the cost of egg
donation, provide egg
storage for women about to undergo therapy harmful
to their reproductive health (for example, chemotherapy
for cancer patients), or allow couples to delay their
reproductive choices. Please see our articles on egg
freezing technology and studies.
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