Cancer treatments induce premature menopause and infertility in hundreds of thousands of women every year. Scientists hope that one day women's fertility can be preserved by removing and freezing ovarian tissue before cancer therapy and transplanting it back later.
Previous research has yielded eggs from ovarian tissue grafted under the skin of a woman's forearm, but the eggs failed to become fertilized. In an experiment described on the Web site of The Lancet medical journal, researchers from Cornell University showed for the first time in humans that a normal embryo can be obtained using the technique.
The scientists, led by Dr. Kutluk Oktay, a reproductive endocrinologist, removed and froze ovarian tissue from one of the ovaries of a 30-year-old woman before she had chemotherapy for breast cancer.
Tests confirmed that she became menopausal after the chemotherapy.
Six years later, the doctors thawed the ovarian tissue, screened it for cancer cells and transplanted it beneath the skin of her abdomen. They gave her hormones to reawaken the tissue.
About three months later, the woman noticed a pea-sized lump at the transplant site. Tests showed that ovarian function, indicated by estrogen production and follicle development, had resumed.
The scientists retrieved 20 eggs from the transplanted tissue. Of eight that were suitable for fertilization, one fertilized normally after her husband's sperm was injected. It developed into a four-cell embryo.
The scientists then transferred the embryo to the woman's womb, but no pregnancy developed.
"Even though the final proof of success of ovarian cryopreservation and transplantation procedure will be a viable pregnancy in a human being, with the development of a human embryo, prospects for a pregnancy and liveborn are now more promising," the scientists reported.
Dr. Johan Smitz of the follicle laboratory at the Brussels Free University in Belgium said the experiment was an advance but the technique still has a way to go. He said it may only be a matter of time before a pregnancy succeeds after this procedure.
But until there is a baby, the research doesn't offer much more than hope, said James Grifo, director of reproductive endocrinology at New York University Medical Center.
"It could be a year, it could be 10 years," said Grifo, who was not involved with the experiment. In the United States, he said, "there is so much regulation around research in this field — mainly for political reasons — that continued progress is hampered."