The findings stand to benefit cancer patients, who can have eggs frozen before embarking on chemotherapy, which could leave them sterile, and couples undergoing IVF treatment who have ethical objections to freezing embryos that might never be thawed.

The results also open possibilities for healthy women in their teens or twenties who do not wish to start a family until they have established a career or found the right partner. High-quality eggs can be put on ice for a decade or more. They could be defrosted and fertilised when the women reach their late thirties or forties, when their fertility would normally be much lower. Britain has 22 clinics licensed to store frozen eggs, and many of them agree to treat patients for purely social reasons.

The research, undertaken in Italy, indicates that women who bank frozen eggs have as good a chance of having a healthy baby as those who choose the more established method of freezing fertilised embryos.

Although the first pregnancy from a frozen egg was achieved in 1986, the procedure has taken almost two decades to become viable. While sperm and embryos can readily be frozen and thawed without suffering significant damage, it has until recently proved difficult to defrost eggs without destroying them.

The defrosting and implantation of frozen eggs had been legal in Britain only since 2000. One baby, Emily Perry, now 2, has been born from a frozen egg in this country, and two women are pregnant at present.

The study, led by Eleanora Porcu, of the AIRA clinic in Bologna, offers the best evidence that the technique is worthy of comparison with other forms of assisted reproduction therapy. Dr Porcu analysed 501 IVF cycles involving 380 women who used frozen and thawed eggs — by far the largest number studied systematically. Some 70 per cent of eggs survived thawing to be fertilised, a much better rate than has been achieved previously. When embryos were implanted, the result was 85 pregnancies and 70 births, all of them healthy. The overall success rate was 17 per cent per embryo transfer. A comparison with a similar group of patients treated with frozen embryos found comparable pregnancy and birth rates.

The results, which Dr Porcu presented last week in Copenhagen, suggest that egg-freezing is as good an option as embryo-freezing.

She said: “My goal was to understand whether this technique works, and I think we can see that it does. There is no statistically significant difference between egg- freezing and embryo-freezing.”

Some couples have religious or ethical objections to freezing embryos that might never be used. Lee and Helen Perry, Emily’s parents, did not want to take this course during fertility treatment because they are Jehovah’s Witnesses.

Dr Porcu said that there is no technical barrier to offering egg-freezing to healthy young women, although she does not find the prospect attractive.

She said: “A young, healthy woman would have to undergo a surgical intervention that is not medically indicated, have pharmacological treatment and sustain possible risks. It is not a walk in the park.”

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