In yet another leap forward in the treatment of infertility, two separate groups of researchers report 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 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 in Italy -- reporting this week believe their methods can indeed eventually be put into widespread use. Each group injected a single sperm directly into each frozen thawed egg -- a process called intracytoplasmic sperm injection -- 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 cryopreserved egg was announced as long ago as 1986, and other, sometimes unverifiable, reports of births from frozen eggs have occasionally surfaced.
U.S. doctors' attempts at replicating the feat have proved futile. But the U.S. and Italian reports 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 method, 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 yesterday that it 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 Bologna, 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.
Pub Date: 10/17/97