主页 > 医学动态 >
【bio-news】(中年)妇女将怀孕希望寄托于先前冷冻
By Dahleen Glanton
Tribune national correspondent
Published January 15, 2007
CHARLOTTE -- Kimberly Cook dreamed of having a family someday, with lots of kids running around and a husband to help her raise them. But like many career-minded women, her job became the top priority, and the man who would share a life with her never came along.
Now, at age 37, Cook has placed her hopes in science. Next week, at the start of her menstrual cycle, she will go to a fertility clinic in Charlotte for a series of shots and pills designed to stimulate the production of eggs in her aging ovaries.
If she is lucky, doctors will be able to extract at least a dozen healthy eggs that will be kept frozen until she is ready to use them.
Freezing technology, or cryopreservation, has been around for decades, with frozen sperm or frozen embryos--fertilized eggs--routinely used in in-vitro fertilization. But freezing fresh, unfertilized eggs is a developing trend in the field of fertility medicine, one that appeals to women who need to delay childbearing for medical reasons such as chemotherapy or radiation treatment or who simply choose to put it off until later in life.
Women who freeze their eggs when they are young would be able to have a child as late as in their 40s or 50s using their own eggs, eliminating the need for donor eggs.
Cook's chances of conceiving a child naturally were slipping fast, hastened by endometriosis, a condition affecting many women of childbearing age where excess tissue forms on the ovaries, making it difficult to get pregnant.
"When I heard the news that I could no longer have a baby naturally, I was truly devastated," said Cook, who owns a marketing company. "I am running out of eggs and I have a small window of opportunity. A lot of people think this is crazy, but now I have hope."
"Infertility is more common these days because women are trying to get pregnant older than in the past," said Dr. Angie Beltsos, medical director of the Fertility Centers of Illinois, which has facilities in Chicago and several suburbs. "I tell women it's like an insurance policy. You might not necessarily need it, but it is good to have in case things don't work out the way you've planned."
Older mothers on the rise
According to the National Centers for Disease Control and Prevention, the birthrate for mothers ages 35 to 49 is at an all-time high.
On the surface, freezing eggs sounds simple. After all, doctors have been freezing sperm for 30 years. But while it might have been easy to trick Father Time, science has shown that it is much more difficult to fool Mother Nature.
Experts said the egg-freezing procedure is still in its infancy. Because of the large water content in eggs, freezing and thawing them is a delicate procedure that has only a 20 percent chance of success, according to Dr. Marc Fritz, chairman of the practice committee of the American Society for Reproductive Medicine.
Worldwide, there have been fewer than 200 documented live births from frozen eggs, and most of those were in Italy, he said.
Doctors in a handful of U.S. clinics that offer the procedure have primarily used a slow-freeze method. Most of the pregnancies resulting from that process, however, have resulted in miscarriages. In recent years, doctors have found greater success with a more rapid freezing technique, called vitrification, in which the water in the egg is replaced with a cryo-protectant that prevents egg damage.
The eggs are then stored in liquid nitrogen until they are ready for fertilization.
"One day we might see egg banks popping up like sperm banks," said Tony Anderson, the embryology lab director at Reproductive Endocrinology Associates of Charlotte, where Cook will undergo the procedure. "This will open up a whole new level of opportunity and freedom for women."
While experts agree that the procedure holds great promise in the future, the American Society for Reproductive Medicine considers egg-freezing experimental and cautions women about getting their hopes too high.
"Currently, the technology cannot deliver on that great promise," Fritz said. "It is our view that it is simply not yet possible to offer any reasonable success with the use of frozen eggs that would allow women to make an informed decision."
Some experts said egg-freezing offers a potential alternative to embryo-freezing, which has long created an ethical debate over when life begins.
Questions remain regarding egg-freezing because of the lack of long-term research. Doctors said it is too early to know whether these babies are prone to birth defects or health problems. In addition, some doctors said, ethical questions could arise over whether clinics should market the procedure to women in the late 30s or 40s, who have less chance of harvesting healthy eggs to freeze.
Insurance doesn't cover it
Egg-freezing--which is not covered by health insurance--can be expensive, costing patients $5,000 to $12,000 to extract the eggs and freeze them and $500 to $1,000 a year to store them. In-vitro fertilization costs an additional $20,000 to $25,000.
阅读本文的人还阅读：
作者:admin@医学,生命科学 2011-03-31 05:11
医学,生命科学网