NEW YORK (Reuters Health) - Frozen eggs can be just as effective as fresh eggs for women trying to become pregnant through egg donation, new research suggests.
Women who were implanted with frozen eggs at a Spanish infertility clinic got pregnant at virtually the same rate as women implanted with fresh eggs, the researchers report in the journal Human Reproduction.
Using frozen eggs, said Dr. Nicole Noyes of the New York University Fertility Center, is much more convenient and potentially cheaper than using fresh eggs -- for both fertility clinics and patients themselves. But because egg freezing is still labeled as an experimental procedure, many egg donation programs still only use fresh eggs, she said.
"Egg freezing is a great thing," Noyes, who was not involved with the current study, told Reuters Health. Once the procedure stops being considered experimental, she said, "This field is going to explode."
Dr. Ana Cobo and her colleagues at the Valencia Infertility Institute in Spain implanted more than 500 women with donor eggs through in vitro fertilization, or IVF. The most technologically advanced of assisted reproductive technologies, IVF involves removing an egg cell from a woman's body, fertilizing it in the lab, and placing it in the woman's womb.
In the current study, half of the implanted eggs were fresh - inseminated just a few hours after they were removed from donors and implanted in recipient women three days later. The other half had been frozen for at least six months before being warmed, inseminated, and then transferred.
Women in the study didn't know what kind of eggs they were receiving - and most of their doctors not involved with handling the eggs didn't know either.
Two and a half months after the eggs were implanted, 44 percent of women who had received frozen eggs were pregnant, compared to 43 percent of women who were implanted with fresh eggs.
"We believe that these data may represent a breakthrough in the current practice of (egg) donation," the authors write.
About 3,000 babies are born from egg donation every year in the U.S., most using fresh eggs.
But there are a few key drawbacks to using fresh eggs for egg donation, Noyes said. The main issue is that doctors have to make sure that the recipient's uterus is ready to receive the egg and the same time the donor is ready to have her eggs harvested.
"Coordinating that from a clinic's standpoint is a little bit hard," Noyes said.
Freezing could also allow a donor's eggs to be split between more recipients, which might make the process cheaper for women trying to get pregnant, Noyes said. The cost of an in vitro fertilization using egg donation is usually around $15,000 to $20,000.
In New York State, Noyes said, donors are paid a standard $8,000 per donation. Doctors don't know exactly how many eggs a donor will produce, so they never prepare more than two women to receive fresh eggs from a single donor, she said. But if a donor produced a lot of eggs, some of those could be frozen and saved for other recipients in the future.
Finally, freezing eggs would give doctors more time to make sure the donor and the egg were disease-free in the same way clinics now do for donated sperm. Eggs probably don't transmit infection, Noyes said, but the possibility that they might remains a concern.
With all the potential benefits of egg freezing, a couple of worries remain. It's possible that eggs could get contaminated while they're being cooled down or while in storage - so freezing should always be done in a sterile environment, the authors say.
And some clinics that don't have a lot of experience with the procedure could have low success rates, Noyes said.
The current study did not follow up on the health of babies born using frozen eggs, but Noyes said her own research has shown that these babies aren't any more likely to be born with birth defects than babies conceived naturally. "That's reassuring," she said. "The litmus test for me is healthy babies."
SOURCE: link.reuters.com/ves58m Human Reproduction, online June 30, 2010.