Women who go through early menopause and cannot have children were offered new hope today after scientists found a way of getting ovaries working again.
The study could pave the way for women to one day have their own babies even though they have gone through the menopause at an early age.
Premature ovarian failure affects 1% of women under the age of 40, with one in 1,000 (0.1%) going through it under the age of 30.
The normal age for menopause is the subject of debate but experts consider early menopause to be before the age of 45.
Possible reasons include chromosome abnormalities, such as a woman with Down's syndrome; enzyme deficiencies, where enzymes damage eggs and prevent the production of the hormone oestrogen; and auto-immune diseases, where the body effectively turns on itself.
Today, scientists at the World Congress of Fertility and Sterility in Munich said their latest work in rats could offer hope for the future.
A team from Cairo University in Egypt used stem cells to restore ovarian function in a group of 60 female rats.
The rats were divided into four groups during the experiment, with the first not given any treatment and acting as a control.
Rats in all the other groups were treated with a chemical to stop their ovaries working, with those in the second group then given injections containing stem cells.
Group three was injected with a saline solution to act as a control, and the group four rats had ovarian failure but received no treatment, also enabling them to act as a control.
The team of experts tested the hormone levels of all the rats to see if they returned to normal following treatment.
Within two weeks, the rats in group two, which had been treated with stem cells, had regained full ovarian function.
After eight weeks, their hormone levels were the same as rats who did not have ovarian failure.
Male stem cells were used so researchers could confirm their presence in the ovaries of the treated group by searching for the Y chromosome.
Professor Professor Osama Azmy, who led the study, said: "The treated ovaries returned to producing eggs and hormones, and we could detect the presence of the stem cells within the newly functioning ovaries.
"What we have done is proven that we can restore apparently fully-functioning ovaries in rats.
"The next step is to look how these rats might reproduce, and to characterise the chromosomes of offspring following treatment.
"We have not yet reached the stage of producing offspring, and so we will need to understand if the baby rats will be genetically related to the mother, or to the donor of the stem cells.
"This is proof of concept and there is still a long way to go before we can apply this to women.
"Nevertheless, this work holds out the possibility that women with premature ovarian failure might be able to bear a baby of their own."