The first pregnancy after an ovarian tissue transplant has been achieved, it emerged yesterday, realising the hopes of fertility scientists that women could one day conceive after the menopause.

The transplant has for some years been the holy grail for fertility experts. The urgent need is to help women whose ovaries will be damaged by chemotherapy and radiotherapy for cancer, but the procedure would also help women who want to spend their most fertile years engrossed in a career.

The 32-year-old woman, who received the transplant in Belgium, is expecting a girl in October. She had some of her ovarian tissue frozen in 1997, prior to radiotherapy and chemotherapy for Hodgkin's lymphoma.

She was treated by the team of Jacques Donnez at the Catholic University of Louvain in Brussels. One of his colleagues will present the results of their work in freezing and restoring the function of the woman's ovarian tissue today at the European Society of Human Reproduction and Embryology conference in Berlin.

Yesterday the team did not want to discuss their breakthrough, prior to publication in an American medical journal, but in an interview with Belgian radio, Professor Donnez said of his patient: "She is pregnant. She lives a life which she could not hope she would be able to live in 1997. She knew that she was going to be post-menopausal, and now she is expecting a child, her own.

"It's her child genetically, growing from her tissue, and she fell pregnant completely naturally, through having sex. She is very happy."

One of the fertility pioneers in this field, Kutluk Oktay, from Cornell University in New York, carried out a similar procedure on a woman treated for cancer, but in March he announced that her attempt to become pregnant had failed.

He acknowledged yesterday that the pregnancy was important, if it was truly the result of the transplant and not due to recovery of the patient's existing ovarian tissue. "The field is progressing rapidly. In the next few years you're going to see lots more pregnancies. Many cancer patients see this as the only bright spot in their dealings with their disease."

Yding Andersen, another leader in the field from the University Hospital of Copenhagen, who is waiting to see if an ovarian transplant patient he has treated becomes pregnant, said: "It's definitely a breakthrough and it has huge implications for a lot of women around the world. If this will lead to the birth of a child, it is fantastic."

His patient, who was also treated for Hodgkin's lymphoma, produced eggs from an ovarian transplant which were fertilised with sperm in a test tube. The embryo has been transferred to her womb.

The woman in Belgium was 25 in 1997 when she had ovarian tissue removed and frozen. Six years later, in February 2003 after she had been declared clear of the cancer, the tissue was transplanted on the fallopian tubes. By June last year, the tissue was producing eggs. A pregnancy test in January was positive and scans in April confirmed a healthy pregnancy.

Ovaries contain millions of eggs when a woman is born, but the numbers diminish over time. The loss accelerates from the age of around 37 and by 50 or so, there are too few to enable her to become pregnant and the menopause sets in.

Storing frozen ovarian tissue in her 20s would allow a woman to make use of her own very productive tissue in later years, when she is ready to have a family.