Freezing a woman's eggs should no longer be considered
"experimental," according to the American Society of Reproductive
Medicine, a move that signals the technique is now standard for
infertility treatment.
The society reviewed data from four
randomized controlled trials and various observational studies that
compared fertilization rates, embryo implantation rates and pregnancy
rates of fresh eggs versus eggs that were frozen using a method called
vitrification.
Overall, frozen (or vitrified) eggs had
fertilization rates between 71 and 79%, implantation rates between 17
and 41% and clinical pregnancy rates (positive pregnancy tests) between
36 and 61%.
The data also showed no increase in birth defects,
developmental disorders or chromosomal abnormalities when in vitro
fertilization cycles were conducted with frozen eggs, leading the
society to declare the technique effective and safe.
"The
technology and technique are getting better, and success rates are
good," said Dr. Samantha Pfeifer, chairwoman of the American Society of
Reproductive Medicine's practice committee. "So with those studies, we
felt comfortable saying there is a lot of information on how oocyte
cryopreservation is improving."
"Vitrification is basically the
solidification of a solution without ice crystallization," said Dr.
Zsolt Peter Nagy, embryologist and scientific director at Reproductive
Biology Associates in Atlanta. "And that's very important."
The
lack of ice crystallization is key to the health of the egg because, as
Nagy explained, "ice crystallization that happens during slow freezing
is the biggest danger for egg ... cryopreservation because ice crystals
can damage the cell membranes, and it results in the degeneration of the
eggs.
"In vitrification, there is no ice crystallization, so basically, you avoid that problem."
Egg
freezing has been marketed as a means for women without fertility
issues to preserve their fertility beyond their peak childbearing years.
Yet the American Society of Reproductive Medicine says its decision to
drop the "experimental" label should not be interpreted as an
endorsement for women without infertility issues to freeze their eggs
for future use.
"We think we should proceed cautiously in using
this as an elective technique, especially in older patients," said Dr.
Eric Widra, chairman of the Society for Assisted Reproductive Technology
practice committee.
"There is an inherent conflict between the
desire to freeze eggs and the need to freeze eggs. Freezing eggs for the
future sounds like a good insurance policy but may not be an insurance
policy that needs to be cashed in."
Widra says that the best way
to conceive is still through natural intercourse at an appropriate age
and that vitrification should be reserved for women and couples with
urgent infertility needs, like patients with medical indications that
they will lose their fertility (perhaps a woman with cancer or a
specific genetic condition), couples going through IVF who don't have
sufficient sperm or couples who are unable or unwilling to freeze
embryos.
Other fertility specialists disagree, arguing that
fertility is different for everyone and that women should consult with
their doctors if they decide to put off pregnancy until their mid- to
late 30s.
"Women unfortunately are getting married later, having children later, facing more infertility problems," explained Nagy.
"Doing
fertility preservation by egg cryopreservation is an option for them
today. It was not an option in the past, but today it is an option."
