Dr. Sherman Silber and colleagues who carried out the operation said that although ovarian transplantation between identical twins would be rare, the technique had great potential for many women.

Soon after the procedure was completed, the previously infertile 25-year-old started having periods and last October she became pregnant for the first time. Wednesday it was reported that the pregnancy had been uneventful and that she had given birth to a healthy girl weighing 8 lbs.

Menopause at the Age of 14

Mrs. Yarber became infertile when she suffered an early menopause at the age of 14, but her identical twin sister Melanie did not.

Melanie has had three children and wanted to donate her eggs so her sister could also become a mother. But this did not work, so she donated some tissue from her healthy ovaries instead.

In last year's operation at St. Luke's Hospital in St. Louis, Missouri, doctors removed the ovary, and separated off the outer tissue that contains the egg-producing follicles.

They then grafted a third of this tissue on to each of Mrs. Yarber's ovaries, while the final third was kept back in case the initial transplants did not work. The risk of organ rejection was minimal because identical twins have the same genes, increasing the chances of success.

Broader Implications

Dr. Sherman Silber and colleagues who carried out the operation said that although ovarian transplantation between identical twins would be rare, the technique had great potential for many women.

"The demonstration that ovarian function can be restored and natural conception and successful pregnancy can be achieved after transplantation of ovarian tissue may have broader implications for young women, such as those who require potentially sterilizing treatment for cancer," he said.

Doctors told the New England Journal of Medicine how it might help advance ways to preserve cancer patients' fertility.

Dr. Allan Pacey, secretary of the British Fertility Society, said: "To be able to successfully graft back a piece of a woman's ovary that was frozen before her cancer treatment would be of great benefit to women diagnosed with cancer at an early age." But he added: "This kind of transplantation would be very, very rare and is not without risk to either party. For the majority of cases, egg donation would be a much easier and safer option."