Dec2007
»News»Newsletter»Timing is Everything:When You Want a Baby Later, December 2007
Timing is Everything:When You Want a Baby Later
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One of the latest techniques of reproductive medicine
allows women
to have children when the time is right.
There are currently two different processes for
conducting oocyte
cryopreservation, also known as egg freezing. One,
vitrification, appears to
be more successful.
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Why Vitrification?
Vitrification is sometimes referred to as flash freezing
because it's a much
more rapid technique than previous methods.
As with traditional in vitro fertilization, the woman will
use fertility
medications with a goal of ovulating many eggs in one
cycle. At the proper
time in the cycle, her eggs will be retrieved through
needle aspiration and
immediately frozen.
While freezing sperm cells has been mastered for
decades now, reproductive
scientists have been challenged by the relative fragility
of egg cells. The
human egg is the largest cell in the body. Just as with
freezing water into
ice cubes, a certain amount of crystallization occurs in
the process. Some
egg cells simply don't survive the experience.
In vitrification, an "antifreeze" type of substance is
used to drop the
temperature so rapidly that ice crystals do not even
form.
With vitrification, more intact eggs result from the thaw.
That leaves more
opportunities to create embryos. With assisted
reproduction, more viable
cells equal more chances to conceive.
When embryologists started using vitrification a few
years ago, they saw
their egg survival rate nearly double.
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After the Thaw
When the woman is ready to try and get pregnant, her
frozen eggs are thawed
and intracytoplasmic sperm injection (ICSI) is
performed. A single sperm
cell is injected directly into the thawed egg cell.
Eggs that are successfully fertilized become embryos
and are transferred
into the woman's uterus.
At this time, several hundred children have been the
result of frozen eggs.
It's not known exactly how long an egg can remain
frozen and still be viable
for fertilization.
Because it's relatively new still, egg freezing might still
be considered
experimental. For this reason, the American Society
for Reproductive
Medicine recommends that women who consider egg
freezing be informed about
the things we don't yet fully understand about the
process, such as the
length of time considered optimal between vitrification
and fertilization.
According to our current knowledge there are no
negative repercussions to
the offspring of frozen eggs used in IVF. In time, just
as with every ART
that's come along (including reliable IVF), enough
studies will have been
conducted to conclude on both the efficacy and safety
of egg freezing.
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In Closing
Egg freezing is most often used at this time for
women who are about to
undergo sterility-causing chemotherapy or radiation
treatment for cancer or
other conditions. It reserves their eggs for later use
with IVF to conceive.
It can also be used by women who wish to "freeze the
biological clock",
returning to use their eggs with ICSI for making
babies when the time is
right financially or otherwise.
I'm happy to answer your questions and discuss any
concerns you may have
regarding egg freezing, vitrification, and delayed
conception.
Sincerely,
Sonja B. Kristiansen, MD
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