Births From Thawed Eggs Reported
In yet another leap forward in the treatment of infertility, two separate groups of researchers report that they have achieved births resulting from eggs that had been frozen before being thawed and injected with sperm.
The long-awaited accomplishment will eventually have widespread repercussions not only for the treatment of infertility but on the continuing ethical debate over the uses and misuses of human eggs and sperm, experts said.
For example, women in their 20s who wish to defer childbearing until a later age--when the chances of getting pregnant decline--could have the option of freezing healthy, young eggs to attempt a pregnancy later in life.
“This is very significant,” said Dr. Alan DeCherney, chief of obstetrics and gynecology at UCLA and editor of the journal Fertility and Sterility. “I think doctors and the public are very sensitive to the implications of this. The problem now is whether this method is reproducible.”
Both groups of researchers--in Atlanta and Italy--reporting this week believe that their methods can indeed eventually be put into widespread use. Each group injected a single sperm directly into each thawed egg--a process called intracytoplasmic sperm injection (ICSI)--instead of relying on in vitro fertilization, in which the egg and sperm are placed in a dish and fertilization is allowed to occur randomly.
A reliable method to freeze human eggs and then fertilize them has proved elusive, despite years of laboratory work and sporadic reports of success. The first pregnancy and birth achieved using a cryo-preserved egg employed the in-vitro method, and was announced as long ago as 1986. Other, sometimes unverifiable, reports of births from frozen eggs have occasionally surfaced since.
American doctors’ attempts at replicating the feat have proved futile. But the two reports this week represent renewed hope that a reliable method to freeze and fertilize eggs is now at hand.
“People have claimed that they had success in getting fertilization from oocytes [eggs], but there were few reputable reports of live births,” said Dr. Mark Sauer, director of the reproductive endocrinology division at Columbia-Presbyterian Medical Center. “Everyone has been waiting for a method that is reproducible. If only one person can get it to work here and there, what good is it? But I think with these [two] case reports, now maybe there is a good chance it will be replicated.”
When frozen eggs are thawed, the outer layer of the egg is often damaged and cannot fuse with the sperm in normal in vitro fertilization. Using the new technique, the sperm is injected into the center of the egg, “bypassing all the problems of the egg membrane being compromised,” said Michael Tucker, the scientific director at Reproductive Biology Associates in Atlanta.
Tucker’s team announced Thursday that they had achieved the birth in August of fraternal twins from frozen, donor eggs. The donor eggs had been encapsulated in a freezer for 25 months before being thawed and fertilized.
The other success--a 1996 birth--is reported by Italian researchers in this month’s issue of Fertility and Sterility, the journal of the American Society for Reproductive Medicine. The Italian team, led by Dr. Eleonora Porcu at the University of Bologna in Italy, reported that they had withdrawn and frozen 12 eggs from a 28-year-old woman. The woman was unable to become pregnant because of problems with her Fallopian tubes.
After four months, the eggs were thawed. Four of the 12 eggs survived the thawing process; the intracytoplasmic sperm injection was performed in each of the four eggs. This was done only after standard in vitro fertilization failed.
Using the new technique, two of the four were fertilized, but only one of those embryos began to grow normally in the lab. That fertilized embryo was transferred to the mother, and the healthy baby girl was born after 38 weeks of pregnancy.
In contrast, Tucker’s team in Atlanta had frozen 23 eggs, 16 of which survived the thawing process. Using the new technique, all 16 were injected with sperm from the husband of the couple seeking treatment and 11 became fertilized. Four of the embryos were placed into the 39-year-old wife. She had sought infertility treatment with donor eggs because her ovaries no longer produced eggs, a condition called premature ovarian failure.
The two embryos that were implanted resulted in the fraternal twins. The children were born healthy.
Freezing eggs has both modest and far-reaching implications, the researchers said. On a more practical note, the ability to freeze eggs could cut down on the number of times a woman undergoing assisted reproductive treatment must have her eggs surgically withdrawn.
Freezing both egg and sperm separately could also eliminate some of the ethical, legal and logistical problems of storing frozen embryos. For example, disputes sometimes arise over what to do with frozen embryos when a couple divorce or one or both members die.
Finally, the ability to store eggs might interest scores of women who are in danger of losing their fertility--because of chemotherapy treatment for cancer or simply due to aging--before they are ready to become pregnant.
“If you have a 25-year-old woman who is looking forward to a professional career, she may want to bank her eggs so that when it does become convenient for her to settle down and reproduce, she has that option,” Sauer said.
“There are also applications that anyone in medicine would jump at: A lot of young people undergo chemotherapy or [hysterectomy] with the knowledge that they will lose their fertility. We always advise men to store their sperm. It would be nice to give women the same hope of future fertility.”
Much more work is needed on the cryopreservation of eggs before the technique becomes widely utilized and egg banks begin to appear, researchers cautioned.
“There are still technical problems associated with oocyte freezing, and the overall survival rate after thawing is poor, as are the fertilization and [cell division] rates,” the Italian researchers noted.
But Tucker said: “My best guess is that within two years this process will be as common as ICSI. I’m looking forward to making this into a consistent, reliable technology so that it will become as important as we think it is.”
