EVERY woman has an unlimited source of human eggs, say US scientists whose research will turn the prevailing view of female reproductive biology on its head.

It has long been thought a woman was born with all the eggs she would have. Scientists now have discovered stem cells in women of reproductive age that can produce eggs, providing a new avenue of treatment for female infertility.

In 2004, a study found stem cells in the ovaries of adult mice could give rise to viable eggs, but the authors faced a backlash from other scientists and people who countered that "humans are not big mice, only if you're in Disneyland".

The work has been repeated by others and mouse stem cell-derived eggs have been shown to give rise to embryos after in-vitro fertilisation.

Professor Jonathan Tilly, from Harvard Medical School, has now found similar cells in the ovaries of adult women. He injected some into immune-deficient mice, to show the human stem cells would turn into viable eggs. They also could be made to mature outside of the body, in vitro.

The frozen ovary tissue came from Japanese women having a sex change, but it was not ethically nor legally feasible to put the new eggs back into a human.

Professor Tilly said the research opened up the possibility that "sometime in the future, we might get to the point of actually having an unlimited source of human eggs".

"A woman could come in and have a small biopsy taken from her ovary for us to retrieve these cells," he said.

"Once we get these cells out, we could take a 100 of them and make a million of them. If we could get to the stage of generating functional human eggs outside the body it would rewrite, essentially, human assisted reproduction."

The research findings are published today in the journal Nature Medicine. Director of the Robinson Institute at the University of Adelaide, Professor Robert Norman, said the research was "very promising".

"It goes against everything we've ever believed," he said.

"It gives hope. I see a lot of people who are about to go through chemotherapy and have parts of their ovary frozen. I'd always thought that was a waste of time, because we can't do anything with it. but if they have stem cells in that tissue and that's what he's implying, there is a lot of hope for the future.

"It also means theoretically women could donate ovarian stem cells to someone else."