New infertility treatment explored in Houston

July 28, 2009 8:14:43 AM PDT
One of the problems of infertility treatments has been the difficulty of freezing and thawing human eggs. It's much more complicated than freezing sperm or embryos. But, successfully freezing eggs could bypass ethical issues caused by freezing and storing embryos.Now, Houston scientists are testing a better method of freezing eggs.

It's hard to believe any part of the human body could live in the brutally cold mist of liquid nitrogen.

But, inside a tube in a liquid nitrogen storage unit are a Houston woman's eggs and what doctors hope will be the first known pregnancy in Texas using frozen eggs.

"Once it's under liquid nitrogen it can never leave the liquid nitrogen or the eggs would die," Dr. Terry Schlenker of the Colorado Center for Reproductive Medicine explained.

The process of freezing human eggs is tricky. Unlike sperm or embryos, which have been frozen and thawed for decades, the success rate for freezing a woman's eggs has been low because the egg is filled with water. When it's frozen, ice crystals that form inside the egg can damage it. Now, a new technique can prevent the egg from forming ice crystals.

"We remove the water from the egg and replace it with a cryoprotectant, or an antifreeze," Dr. Schlenker said.

Dr. Schlenker came to Houston IVF, located at Memorial Hermann Hospital, to teach the technique.

"At the very end we completely dehydrate them and they completely collapse, and that's the point where we place them on the cryo top and we plunge them into liquid nitrogen," Dr. Schlenker explained.

Successfully freezing eggs would allow a young woman with cancer to preserve her eggs before chemotherapy and radiation treatments. Women nearing 40 could also preserve their fertility. And, freezing an unfertilized egg avoids the ethical dilemma of freezing an embryo. With the antifreeze methods, it's getting easier to do that.

"The eggs survive very well and become embryos pretty much like fresh eggs, so it's really revolutionary," Dr. Schlenker said.

The answer may come soon for the first Houston study patient. She hopes her newly frozen eggs will result in a pregnancy.

Another use for a successful egg freezing technique is that it would allow donors to freeze eggs and bank them for recipients to use at a later time. The cost is about the same as for an in-vitro fertilization cycle, about $10,000.

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Christi Myers is ABC13's Healthcheck reporter.

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