Christina Chale has ticked a lot of boxes for a successful life. “I own my own flat, I did my master’s last year, I’m where I want to be in my career,” she says happily. The PR account director from Brighton travels abroad regularly, visiting her mother in Tanzania and her sister in America. She enjoys art galleries and museums, and is a keen runner. But there is one cloud on the horizon.

Chale is single, in her thirties, and aware that with every tick of her biological clock her chances of having children are receding. “I’ve just been rushing through life, but in the past year and a half or so it’s become more of an issue. It’s on my mind now.”

Even modern medicine, so skilled at freezing sperm and performing IVF, would be of little use to her - until now. With present techniques, freezing a woman’s eggs for use later is too risky except in cases where there is no other option. But this month all that will change.

Two leading British fertility clinics are to start offering a new technique for freezing eggs that has shown such promising results that they are marketing the treatment to women who simply want to put motherhood on hold. If women want to pursue their careers or find Mr Right before trying for a child, they will, in effect, be able to freeze their biological clock.

Dr Simon Fishel, managing director of Care Fertility, which has about 10 fertility clinics across Britain and will be offering one of the new vitrification techniques, said: “Until now, the conventional technology has been used to freeze eggs mainly only if it is a dire last resort for women who want to preserve their fertility before having cancer treatment.

“But, with this new technology, which is almost as efficient as fresh IVF, it might make a lot of sense for women in their twenties to have their own bank of eggs stored if they are considering not having a family until their late thirties.”

Will it be a boon to women, allowing them more freedom to balance careers and families? Or is another technological step on the way to a dubious new world of mechanised birth? Fishel is aware of the potential for controversy:

“Society will have an interesting debate. People are going to say how disgraceful that women can go on and have their careers and not worry about having a family until they are 40 years of age just because they have got a whole bank of stored eggs.

“But the tragedy for women is that, if a man decides in his mid-forties that his career is established and he wants to settle down and have a family, he can do that. But the poor woman is faced with the prospect that this is not going to be possible for her.

“I believe this new technology makes it ethical for us to offer egg freezing to all women.”

THE first woman in Britain to give birth to an “ice baby” - a child born from a frozen egg - was Helen Perry, whose daughter Emily was born in 2002. Perry suffered from blocked fallopian tubes and was at high risk of a condition called ovarian hyperstimulation syndrome. To preserve her fertility she had eggs removed and frozen until she needed them.

But the procedure was fraught with complications and risks. Eggs are more fragile than sperm, fewer of them are produced and they contain more water. When they are frozen the water can form ice crystals that damage the egg when it is thawed.

The low success rates of such traditional egg freezing have discouraged doctors from offering the treatment to healthy women. Some believed it would have been unethical - because healthy women who chose to freeze eggs and missed out on natural conception might later discover their frozen eggs were too damaged to be fertilised.

Tessa Darley, a 37-year-old local government officer from Glasgow, knows the risks. She decided to freeze some eggs because early menopause runs in her family, but she is realistic about the chances of success if she tries to have them fertilised.

“I’ve got six eggs, and with the technology at the moment, it’s only about one in eight that work,” she says. “I’m realistic about that, but it still means I’ve got an extra chance.”

Under the new techniques, however, the chances of a thawed egg being undamaged and capable of fertilisation are much higher: up to 90% or 95%. The new methods have resulted in pregnancy rates comparable to the use of fresh eggs in IVF of 30%-40%.

The new vitrification system involves gradually removing water from the eggs by dipping the cells, one by one, into dehydrating solutions. The dehydrated eggs are then plunged into liquid nitrogen, freezing to - 196C within seconds.

It’s so effective that Professor Gedis Grudzinskas, medical director of the Bridge Fertility Centre, said: “This technology can now be considered to be very useful for women for personal and social rather than for medical reasons.”

He suggests egg freezing will offer the sort of reproductive choices to women that the con- traceptive pill brought when it was introduced in the 1960s. “Egg freezing gives women more choice, the chance to delay having children until the time that is right for them.”

Women who want to focus on their career, or who have yet to find a suitable partner, could freeze eggs as an insurance policy or for use in their late thirties, forties or beyond. Female fertility falls sharply after 35, yet the age at which women are having children in Britain is rising. In 1971, the average age for giving birth to a first child was 26.2. In 2006, it was 29.2.

Childlessness is also rising. Only one in 10 women born in 1941 remained childless; but of women born in 1961 one in five has remained childless. A recent report suggested that a third of female graduates will never have children.

Personal desires and changing society mean that more women expect to have it all - and often leave it late to have children.

“People have more things they want to do first: travelling without a child, for example, or building up their career,” says Linda Blair, a clinical psychologist and associate fellow of the British Psychological Society.

“To say I’ve got to get it all out of the way before I have a child - I think that’s a little unrealistic.”

But not if freezing eggs works as scientists claim.

HOWEVER, the possibility of being able to delay pregnancy beyond the normal ages of conception is no simple panacea.

Josephine Quintavalle, of the campaign group Comment on Reproductive Ethics, said healthy women would put themselves at unnecessary risk. Women who want their eggs removed and stored must take medication to prompt their ovaries to produce multiple eggs.

Quintavalle also argues that if delaying motherhood became routine, the structure of family support and society would change.

“To imagine that IVF can be an alternative to natural reproduction for healthy women is an absurdity,” she said. “The chances of children having grandparents becomes ever more remote. This will undermine the whole structure of society.”

There is no doubt that older mothers face certain challenges. Chasing a toddler around in your late forties will be more exhausting than in your mid-twenties, even if people are staying fitter longer. Older mothers are more likely to suffer from complications such as diabetes and preeclampsia. Births are often more difficult and there are more instances of caesarean sections.

However, young eggs implanted in an older woman should suffer no higher risk of Down’s syndrome and other genetic disorders often associated with older births. Despite the risks, the boundaries are being pushed back by new IVF techniques.

Patricia Rashbrook, a psychiatrist from East Sussex, gave birth in July 2006 at the age of 62; and in December 2006 Carmela Bou-sada, a 66-year-old from Cadiz in Spain, gave birth to twins after IVF treatment.

From a career viewpoint, Catherine Rogan from the charity Working Families says there are pros and cons to having children early or late. “There is no ideal age. If you’re in a job that’s not too taxing and more junior, having a year off may well not be a problem. But if you’re in a more senior position, it can be more difficult having the time off and then coming back in. “

The flipside of that is that if you’ve been working hard and well for 10 years, you can point at your track record and employers will be able to trust you.”

However, Susan Anderson, director of human resources policy at the Confederation of British Industry, thinks women would be more likely to go down the freezing route over relationships than careers. “I would guess that you’re more likely to find that women haven’t met the right man rather than don’t want to take the time off work,” she said.

There are much broader controversies, too. With world population expected to hit 7 billion in 2013, is it really necessary to extend fertility by such artificial means? For many women, however, their dreams of cuddling a child of their own outweigh such wider concerns.

Chale, for one, doesn’t see why she should give up her hopes of having children and is prepared to become a single parent in the future - using frozen eggs if necessary. “Why should I give it up? I am capable of being a really great parent,” she said. “I don’t want to give up that chance yet.”

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