Belgian scientists have successfully performed an ovarian tissue transplant between non-identical sisters for the first time.
Teresa, left, received ovarian tissue from her sister
Teresa Alvaro's ovaries had failed due to damage caused by medical treatment.
Following the transplant she started to menstruate again, and after a year doctors were able to recover two eggs from her ovaries.
The journal Human Reproduction reports that these were fertilised to produce two embryos.
Ovarian tissue transplants have been carried out before - but only between twin sisters with the same genetic make up.
In 1990 at the age of 20, Ms Alvaro received extensive treatment for beta-thalassemia, an inherited blood disorder, including chemotherapy and radiotherapy, and a bone marrow transplant from her young sister Sandra.
Egg donation rejected
The treatment was successful, but caused complete ovarian failure.
In 2005 Ms Alvaro consulted Professor Jacques Donnez, of the Catholic University of Louvain in Brussels, about the possibility of an ovarian tissue transplant from her sister to give her the chance of becoming pregnant.
She rejected the idea of an egg donation from her sister, as she wanted to be "responsible" for maturing the egg in her own body, and did not want her sister to have to take ovary-stimulating drugs.
The fact that Teresa had already received tissue from her sister was in her favour.
Her sister's cells had mixed with her own, and although they were genetically different, they were able to co-exist successfully together - meaning Teresa would not have to take drugs to stop her sister's ovarian tissue being rejected.
Teresa received three small sections of ovarian tissue from her sister in an operation in February 2006.
The sisters were discharged from hospital the day after surgery, and after six months Teresa started to menstruate again, indicating ovarian function had been restored. Her menstrual cycles have continued ever since.
A year after the transplant, the doctors retrieved two mature eggs from her ovary and fertilised them with her husband's sperm.
One of the resulting embryos developed to the two-cell stage and the other to the three-cell stage, but then both ceased to develop further, and so the embryos were not transferred to her uterus.
Professor Donnez said: "We do not know why the embryos ceased to develop, but this also happens during normal cycles of IVF.
"The patient is planning more IVF attempts in the future."
He said that it was too early to say whether this procedure would ever be successful enough to result in a baby.
However, the work did give hope to women who had not had an opportunity to freeze either their eggs or their ovarian tissue.
It also emphasised the importance of leaving at least one ovary in place during any treatment because the ovary offered an excellent site for a subsequent transplant of ovarian tissue.
Teresa Alvaro said: "The operation was a success. I can get pregnant the natural way. That's something I could never have hoped for a couple of years ago."
Dr Allan Pacey is senior lecturer at the University of Sheffield and Secretary of the British Fertility Society.
He said: "The science that underpins this type of transplant will be of great benefit in developing realistic fertility preservation options for young women who want to preserve their fertility prior to cancer treatment.
"In such cases, most women will want their own ovarian tissue removed and frozen before chemotherapy then replaced after their treatment has finished.
"But woman to woman transplants like this may become common if suitable donors are willing to come forward."