By Ben Hirschler

LONDON, July 2 (Reuters) - The first test-tube baby created from an egg matured in the laboratory and then frozen has been born in Canada, in a breakthrough offering hope to women with cancer and others unsuited to normal IVF treatment.

The baby is doing well and another three women are pregnant by the same method, researchers told a medical meeting in Lyon, France, on Monday.

Conventional in vitro fertilisation (IVF) involves using high doses of expensive hormone drugs to stimulate the ovaries to produce multiple mature eggs.

But some women seeking to preserve their child-bearing capacity may not have enough time to undergo ovarian stimulation or may have a condition that makes it dangerous, such as hormone-sensitive breast cancer.

For these patients, ripening eggs in the lab -- so-called in vitro maturation (IVM) -- makes sense. Until now, however, scientists have never frozen, thawed and then fertilised a lab-matured egg. This multi-step process increases significantly the flexibility of fertility treatment.

"We have demonstrated for the first time that it is possible to do this and, so far, we have achieved four successful pregnancies, one of which has resulted in a live birth," Hananel Holzer of the McGill Reproductive Center in Montreal said in a statement.

The research is still at an early stage and has not yet been proven in cancer patients, he told the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE).

But Holzer and other experts believe it has the potential to become one of the main options for fertility preservation.

Women diagnosed with cancer are likely to be the main beneficiaries, since cancer treatment can make them sterile and they often have no time to take fertility drugs.

At present, there is the experimental option of having ovarian tissue removed, frozen and transplanted back later. But this brings with it a theoretical risk of re-introducing cancer.

Holzer tried his new technique on 20 infertile women with polycystic ovary syndrome, a leading cause of infertility.

Joep Geraedts, ESHRE's chairman elect, said the resulting four pregnancies, or 20 percent success rate, was "quite good".

"If this works in cancer patients, it might ultimately be possible to do this in all women that undergo IVF or assisted reproduction because then you don't need to bother them with hormones," he told Reuters in a telephone interview.

It could also save money, since treatment with hormone drugs can cost thousands of dollars. Leading makers of fertility drugs include Merck Serono <SEO.VX> and Akzo Nobel's <AKZO.AS> Organon unit, which is being acquired by Schering-Plough <SGP.N>.

Geraedts said there should now be large-scale clinical trials to assess the new procedure definitively.

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