For the first time, doctors appear to have restored fertility in a menopausal woman by reimplanting into her abdomen several pieces of her ovaries that had been removed and frozen when she was younger.

The experimental procedure, performed on an American ballerina, could lead to greatly expanded reproductive options for women by allowing them to become pregnant years or decades later in life than is now possible, doctors said.

That option is generally restricted to men, because sperm can be frozen indefinitely while eggs do not tolerate freezing well. Frozen embryos can survive for many years, but that approach requires a woman to choose in advance the father of her future child.

The ballerina, who is now 30 and went into early menopause after her ovaries were removed for medical reasons, has not tried to get pregnant yet, so it's too soon to say she is truly fertile. But all indications are that her reimplanted ovarian tissues are functioning well and can produce mature eggs on a monthly cycle, her doctors said.

"She actually ovulated and then she menstruated," said Kutluk Oktay of the New York Methodist Hospital in Brooklyn, who led the effort with Richard Gosden of the University of Leeds in England.

The results are scheduled to be presented on Monday at the annual meeting of the American Society for Reproductive Medicine in Toronto but were leaked on Wednesday to newspapers in Britain, which touted the work yesterday in front-page headlines declaring the "end of menopause."

Among the first to take advantage of the method will be young women undergoing treatment for cancer, Oktay said, which can poison the ovaries and render women infertile. Scores of such patients in the United States and England already have had parts of their ovaries frozen in the hope that successful reimplantation will someday be available. Until now, however, the method had only been proven wholly successful in a single experiment performed on a sheep.

In the long run, doctors expect a much greater demand from healthy young or middle-aged women who want to save a clutch of youthful eggs in "suspended animation" until they are ready to become pregnant later in life.

"The demand for the medical applications like cancer is limited but important," said Robert J. Stillman, medical director of the Shady Grove Fertility Reproductive Science Center in Rockville. "But the demand for [family] planning is immense."

Research has shown that the primary reason postmenopausal women fail to become pregnant is because their ovaries and eggs have grown too old, Stillman said, not because the women are biologically incapable of maintaining a normal pregnancy or carrying a fetus to term. But ovarian tissues, and the many immature eggs nestled within them, seem not to age when kept frozen in liquid nitrogen.

Ovarian tissue removal is a relatively simple surgical procedure, performed on an outpatient basis under general anesthesia. An instrument called a laparoscope is inserted through a small incision above the pubic area. The tissues must be frozen gradually in a specialized regimen that is still being improved but already is available at several fertility centers, including the Genetics & IVF Institute in Fairfax.

After the tissues are reimplanted, a woman could get pregnant and give birth normally as long as her fallopian tubes and uterus are intact.

The ballerina, identified by the Reuters news agency as Margaret Lloyd-Hart of Arizona, had one of her ovaries removed when she was 17 because it had developed cysts. The second was removed when she was 28. But the woman, who is married, knew she might want to become pregnant someday, so she arranged to have tiny strips of her second ovary frozen.

Six months later, unhappy with various side effects of the hormone replacement therapy she was on, the woman contacted Oktay about having some of her tissues reimplanted.

Oktay and his colleagues stitched 80 of the tiny tissue strips -- each of them 5 millimeters to 10 millimeters long -- onto a triangular frame, about 2 1/2 inches wide, made of a surgical foam that gradually dissolves in the body. Then they sewed the structure into the woman's pelvic cavity, near where one of her ovaries had resided.

The graft quickly attracted a new blood supply and started to produce various female hormones. Three months later, the team stimulated the tissues with extra doses of the egg-maturing hormones that are typically used for in vitro fertilization. One egg matured and was released by the ovary, as would be expected in a fertile woman. But the dancer decided she did not want to become pregnant, so doctors did not retrieve the egg for fertilization with sperm.

Meanwhile, Oktay and others said, researchers are also improving their ability to freeze human eggs for later use.

Two years ago a Georgia woman became the first in the United States (and perhaps the third in the world) to give birth to a child from a thawed egg. And several researchers are scheduled to describe additional successful births from frozen eggs at next week's meeting of the American Society for Reproductive Medicine.

Medical experts and ethicists have expressed concern that the emergence of fertility-prolonging treatments such as these might lead to a new generation of children born to very old mothers who might not live to see their children make it to high school. Yesterday Stillman said he hoped the technique would not be "abused" as a mere "social convenience," but he acknowledged that it would be unfair to deny women an option that men have long had.

"Many men getting vasectomies store sperm beforehand as a backup in case they change their mind, as they often do," Stillman said. "We have to be equally supportive of allowing women to do the same if the technologies have caught up."

Second Chance

An experimental procedure in which doctors remove and freeze pieces of a woman's ovaries and reimplant them later appears to have restored fertility in a menopausal woman.

1. Strips are removed from a woman's ovaries . . .

2. . . . and frozen to minus 320 Fahrenheit.

3. Years later they are thawed and attached to a frame . . .

4. . . . and implanted near the fallopian tubes, where they begin to produce eggs again.

SOURCES: Staff research, Ultimate Visual Dictionary of Science