A method of storing human eggs which allows women to postpone motherhood is as safe as conventional IVF treatment, research suggests.

A Canadian study, published in the journal Reproductive Biomedicine Online, looked at 200 children conceived using "vitrified" eggs.

The technique involves rapid freezing, and could also help women whose fertility is threatened by cancer.

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Although sperm and embryos are often frozen and successfully thawed, early ways of freezing eggs have proved far less successful.

The formation of ice crystals in the liquid within the egg can damage its structure, rendering it unusable.

"Vitrification" involves the removal of water from the egg, the addition of an "antifreeze" solution, then "flash freezing" in liquid nitrogen.

It is suggested that up to 95% of eggs survive the process, compared with 50% to 60% using older methods.

It is already available at a handful of clinics in the UK, costing up to £3,000, plus a small fee for annual storage.

Women have a fixed number of eggs to last them a lifetime, and fertility drops sharply from the late-30s onwards as the number of eggs dwindles.

Effective and safe egg-freezing methods would allow eggs to be harvested, then used to produce an IVF pregnancy later in life.

Aside from the wish to delay motherhood beyond their 30s and 40s, some women may use this technique for medical reasons, perhaps if they are facing cancer treatment which will render them infertile, or a premature menopause.

The researchers, from McGill university in Montreal found that the rate of birth defects among the 200 children conceived using vitrified eggs as 2.5%, roughly the same as in natural pregnancies and IVF.

Research call

Dr Allan Pacey, the secretary of the British Fertility Society (BFS), said that more, similar, studies would be needed before the safety of the procedure could be established.

"The British Fertility Society would say that this should only be offered in the UK as part of a controlled trial.

"We are getting close to the stage where I would be comfortable offering this to women who are about to have chemotherapy for cancer."

He said that, although the BFS had no policy on using egg-freezing for "social" reasons, his personal view was that there were no ethical problems with offering women the chance to plan their families in this way.

"We have been offering men the chance to freeze their sperm for this reason for years now, and I don't really see any great difference between the two.

"Why shouldn't women have the same opportunities as men?"

(BBC)

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