In the 1990s, in experiments involving sheep and mice, Dr Roger Gosden, working at the Department of Physiology and the Centre for Reproductive Biology in Edinburgh, and Dr Jill Shaw, of the Centre for Early Human Development in Melbourne, succeeded in removing pieces of ovary, cutting the tissue into slices 2 mm thick, freezing the slices and then transplanting the tissues back to the same animal some time after that animal -- in the course of the experiment -- had had all other ovarian tissue removed.

Ordinarily this should have been the end of ovarian function (and of course fertility) for these animals. In the majority of the animals the stored tissue, transferred either to under the capsule of the kidney (a very vascular spot) or back to the region where the ovaries had been, was able to regrow and to function normally, including ovulation. In some of the animals where the tissue was back where the ovaries should have been, the animals were fertile.

The development of "ovarian slice freezing" in the late 1990s promised the preservation of ovarian follicle function for women faced with a disease or treatment that threatens the survival of their ovaries, such as radiation treatment or chemotherapy for cancer or even endometriosis (if it is bad enough to threaten the ovaries).

It was also hoped that preserving ovarian follicles at a young age might become an option for women prescient enough to foresee a long career standing in the way of early pregnancy and family building.

Although the numbers of follicles that survive the storage process is just a fraction of those removed, the experiments with sheep show that fertility can follow.

Unfortunately, to date, no successful regrafting of ovarian slices has been reported in humans.

Several researchers have shown that the follicles can, if left long enough (up to eight months after the graft) produce estrogen and even, occasionally, a retrievable egg; but normal fertilization and embryo development has not yet followed, and still (in 2002) no baby.

Maybe the number of primordial follicles is, for humans, just too small in such a tiny slice to allow the probably tiny fraction of them that have full developmental potential to have had enough chance of having been included in the sample.

In other words, perhaps all that has been achieved for these women so far is to put them from a menopausal situation into a perimenopause, when egg numbers are low, fertility is almost non-existent, and cycles are erratic.

Dr Gosden is now experimenting with freezing whole ovaries.