We have demonstrated that whole organ transplantation is feasible

Professor Roger Gosden

Scientists have previously been able to store and freeze tissue samples.

But until now it has not proved possible to freeze and store whole organs because the freezing and thawing process does too much damage.

The researchers carried out their research on rats.

Pregnant rodent

They removed and stored the creatures' ovaries in liquid nitrogen, then successfully transplanted them into rats that were genetically identical.

Although the transplanted ovaries were less efficient after freezing, more than half ovulated normally and one recipient became pregnant.

Lead researcher Professor Roger Gosden, of the Eastern Virginia Medical School, US, said that if the technique could one day be applied to humans, it would offer an option to women and children who would otherwise be sterilized by chemotherapy.

It might also be used to reduce the risk of premature sterility in women with other medical conditions.

Advances in freezing techniques could also make it possible to store and successfully transplant other organs. At present, freezing tends to cause irreparable damage to the blood vessels.

Professor Gosden told BBC News Online: "The take-home message is that we have demonstrated that whole organ transplantation is feasible.

"The frozen ones were not all successful, but that is not surprising because 50 years after the first successful sperm freezing results are still not perfect."

Professor Gosden said it would be more difficult to freeze human organs successfully because they were larger.

However, the blood vessels, being larger, would potentially present less problems during surgery.

The research is published in the magazine Nature.