By Michelle Roberts
BBC News health reporter in Copenhagen
Scientists claims there is now definite proof that transplanted frozen ovarian tissue can restore a woman's fertility after cancer treatment.
Tamara Touirat is the first baby to be born to a woman after an ovary transplant
Israeli researchers told a European fertility conference in Copenhagen that a second woman had become pregnant after an ovary tissue transplant.
A Belgian woman last year became the first to have a baby after undergoing the treatment.
But sceptics say the women's own ovaries could have begun working again.
Doubts were raised last year when a Belgian woman, Ouarda Touirat, became the first woman to have a baby after ovarian tissue, removed before her cancer treatment, was put back into her body.
Some experts said her existing ovaries could have begun working again and produced an egg, rather than the transplanted tissue.
But the Israeli researchers say the woman they treated had undergone a premature menopause, so the egg which was fertilised for her pregnancy must have come from transplanted tissue.
Researchers from the Chaim Sheba Medical Centre, said she had had some of her ovarian tissue frozen after she had undergone a first course of chemotherapy for non-Hodgkin's lymphoma. Her subsequent courses of chemotherapy pushed her into early menopause.
Later, when she was declared clear of the cancer, she had her strips of frozen ovarian tissue replanted back into the ovaries.
While the original ovary tissue did not respond to IVF drugs, the transplanted tissue did.
It was from this tissue that the doctors say they harvested the eggs needed for her IVF treatment.
They are due to publish their findings in the New England Medical Journal.
Dr Francoise Shenfield, a fertility expert at University College London, UK, said: "This is a very convincing study.
"All the data fits. The evidence is very clear."
Dr Sherman Silber, the US scientist who reported earlier this month that he had helped a woman who became infertile in her teens to have a baby girl using healthy donor ovary tissue from her identical twin sister, said all the evidence taken together proved beyond reasonable doubt that the transplants were restoring the fertility.
"The scientific community was very sceptical about the Belgian report because the woman had some ovulatory cycles before the scientists put the frozen ovarian tissue back.
"So maybe the pregnancy was due to her residual ovarian tissue.
But he said the Belgian and Israeli research, along with his own work, were conclusive.
"Transplanted ovarian tissue unquestionably results in normal ovulation and pregnancies."
He said the latest research also demonstrated that it was still beneficial to preserve tissue even if a woman had already started chemotherapy.
However Dr Shenfield cautioned that it would be important to ensure the ovarian tissue removed and thawed did not contain any cancer cells that might cause a relapse when transplanted back.