Scientists in the United States have produced the first ever live birth from transplanted ovarian tissue.
By Ania Lichtarowicz
BBC health reporter in San Antonio, Texas
The procedure carried out in a rhesus monkey could, researchers say, be used for humans.
A healthy rhesus monkey was born after the transplant
The development gives new hope to women who have become infertile following cancer treatment.
The breakthrough was announced at the American Society for Reproductive Medicine (ASRM) conference in San Antonio.
Scientists from Oregon National Primate Research centre removed part of the ovary in a rhesus monkey and transplanted it to another part of the body.
When eggs matured on the transplanted tissue, they were collected and fertilised in the lab.
The resulting embryos were then transplanted back into the womb and one developed into a healthy baby monkey.
This technique, the scientists say, could be adapted for use in humans.
"It's a great step forward," commented Professor Nancy Klein of Washington University in Seattle.
"The technology could allow women to preserve fertility in cases where they are going to lose it prematurely - say in the case of women undergoing chemotherapy for cancer."
Women and young girls who are diagnosed with cancer could have ovarian tissue frozen and transplanted years later when they wanted to conceive.
However, Professor Klein is more sceptical about the idea of healthy women storing ovarian tissue so that they could conceive later in life, overcoming the menopause and having babies in their late 40s or 50s.
"We're far away from that," she says.
"There is a great loss rate of the number of eggs that will survive the freezing process, and so it requires usually the removal of a whole ovary. Women who are already in their mid-30s probably won't have enough eggs to make that a feasible approach."
Alison Murdoch, from the British Fertility Society, said that the treatment was a "big breakthrough" and offered a realistic prospect of helping women who faced losing their fertility to cancer treatments.
She said: "Men in this position can store their sperm and then have children after treatment has ended, but the technology has not existed for women."
She said that there was still likely to be a delay before the treatment was readily available for humans - as there were still questions about safety that needed to be resolved.