Last week, anonymous egg and sperm donation ended in Britain. So will more childless couples be forced to go abroad for the chance to conceive?

A sperm's journey to the egg has never been an easy one, but today it can involve much more than a race to the Fallopian tube. Natalie Parker, 41, from North London, is five months pregnant with a child conceived with her husband's sperm and an egg donated by a Romanian woman. She flew to the Globalart clinic in Romania in October last year to have the embryo transferred into her womb, after waiting three years for an egg donor in Britain.

A sperm's journey to the egg has never been an easy one, but today it can involve much more than a race to the Fallopian tube. Natalie Parker, 41, from North London, is five months pregnant with a child conceived with her husband's sperm and an egg donated by a Romanian woman. She flew to the Globalart clinic in Romania in October last year to have the embryo transferred into her womb, after waiting three years for an egg donor in Britain.

Human gametes are hardy creatures. Both sperm and embryos, although not eggs, can be frozen, shipped between continents, thawed and still fulfil their raison d'être. Natalie's husband's sperm were frozen and flown out to Romania in advance of her visit so that the embryo could be prepared for her arrival. So far, only a few British couples have used globetrotting gametes to conceive, but a change in the law this month means that more may follow.

Last week, anonymous sperm and egg donation ended in this country. This is good news for donor-conceived adults who want to know where they come from. But, at least in the short term, it is bad news for couples wanting to conceive using donated gametes - especially donated eggs. British clinics are already reporting that couples are waiting up to five years for eggs. The wait is expected to be longer now donors must be prepared for a knock on the door once their biological children reach 18.

Many infertile couples are expected to decide that they can't afford to wait that long; that they need to find a solution to their fertility problems now. "Because people are clever and because the world is round, people will find ways around the shortage in donated eggs. They will go abroad to get eggs," says Professor JG Grudzinskas, the medical director of the Bridge Centre, a private fertility clinic in London, which organised Natalie Parker's trip.

The Bridge Centre has run the scheme with Globalart since early last year, when news of the end of donor anonymity broke. So far more than 50 couples have taken advantage of the programme, paying more than £7,000 each. Patients either travel to Romania for treatment, as Natalie did, or remain in Britain. In this case, the husband's frozen sperm is sent to Romania to fertilise the donated egg and the resulting embryo is then frozen and flown back to the UK for implantation in the wife's womb.

Across Eastern and Southern Europe, clinics like Globalart are preparing to receive British couples in search of a ready supply of donated eggs - and cheaper treatment. "I went to a conference in London two months ago and realised that there was a huge demand for fertility treatment using donated eggs in Britain," says Dr Ales Sobek, who runs Fertimed, a private fertility centre in Olomouc, Czech Republic. Last week, three British couples booked in for treatment at Fertimed. It recruits egg donors from the local area and has no problem doing so.

One clinic in Crete is offering childless couples an "IVF holiday", which includes treatment, transfers and accommodation. Fertility Center Chania offers the complete package for around €3,000 (£2,000), depending on the treatment required. Since the scheme was launched last year, only a handful of British couples have taken advantage of it, but Ioannis says that more are on the way.

Once abroad, couples are not covered by British law and, at some clinics, can choose the sex of their child or conceive when they are into their fifties or even sixties.

Nikki Chenery, 34, from Devon, travelled to Spain two years ago so that she could select the sex of her children. Already the mother of four boys, she was delighted to conceive twin girls, now 18 months old. "It was worth it beyond doubt," she says. "The rewards far outweighed the emotional and physical effort. If you want a child badly enough, my advice is to go for it."

But couples risk stepping into a legal, moral and medical minefield once they leave the country. "We don't recommend that anyone goes abroad because, if you do, you will have no control over the treatment you receive," says John Paul Maytum, a spokesperson for the Human Fertilisation and Embryology Authority (HFEA), the Government's fertility watchdog. "For example, there's no guarantee about the health of the woman donating the eggs. So there are risks for the woman carrying the eggs and the child born as a result."

And what of children conceived using donated eggs from abroad? The Romanian scheme run by the Bridge Centre abides by the "full spirit of HFEA regulations", according to a spokesperson. This means that, from this month onwards, children born from donated eggs from the Globalart centre will have the right to discover the identity of their biological mother once they reach 18. However, there are no such guarantees at other clinics. Donation in the Czech Republic is anonymous.

Sarah Jones, from South Wales, was conceived 25 years ago using donated sperm. The records of her conception have been lost and so she will never be able to find the identity of her biological father. "I will never know the origins of my genetic identity," she says. "It's the hardest thing to come to terms with, especially as I will pass these genes onto my own children."

It is this anguish that the new British legislation is designed to dispel. Donor conception will become very similar to adoption in that, once donor-conceived children reach 18, they will be able to contact their donor if they wish. Jones stresses that couples who go abroad for fertility treatment must consider the effects their actions will have on their children. "Parents need to realise their child will become an adult with its own opinions and emotional needs. If I knew that my parents had actively chosen to deny me knowledge of my biological father, I would be devastated," she says.

Even if clinics do keep records of their donors, a child's discovery that its mother is Romanian, Czech or Cretan will not necessarily be easy to come to terms with. The women who donate their eggs, undergoing a painful, invasive procedure to do so, may be from a very different background to the child born as a result.

There are fears that women who donate their eggs in countries such as Romania and the Czech Republic do so, despite the unpleasantness of the procedure, because they have few other ways of earning money. At the Globalart clinic in Romania, women are paid between £150 and £200 in expenses. In Britain, HFEA guidelines mean a woman can be paid no more than £15 plus expenses (this can amount to as much as £500).

A spokesman for the Bridge Centre says that £200 is not enough to persuade Romanian women to donate their eggs merely as a means to alleviate poverty. The reason why Romanian women donate in far higher numbers than British women is to be found in their national character, he believes. "There is something in the Romanian culture," he says. "They have an altruistic streak."

Couples who conceive at the Globalart clinic are able to find out the age, physical characteristics, occupation, education and interests of their donor. This is far more information than couples in Britain receive. Even under the new legislation, couples will only be allowed basic details such as a donor's ethnicity, eye colour and hair colour. It is the child, not the parents, who will have more rights for information.

This lack of information - and also the current shortage of both men and women who have agreed to be known donors in the UK - has prompted another, less common, form of fertility tourism. There are several British couples who have decided to go to the United States because, in the land of opportunity, you can find out as much as you want about your donor and pass that information on to your child.

Diana and Geoff Stevenson, from Wales, discovered that they could not have children two years ago. "I was completely devastated when I found out that I couldn't father children," says Geoff. "My first instinct was that, if we did use a sperm donor, no one would have to know. But, after a lot of soul-searching, we decided that we had to use a known donor.

"I suppose we are making a selfish decision by trying to have children," he says. "We are saying that we do have a right to have a child, even though nature says that we don't. So, we felt that if we were going to make that selfish decision, we had to make sure our children didn't suffer as a result; that they would be able to find out the truth about their genetic heritage."

The couple approached a clinic in Boston, which offers a scheme whereby donor-conceived children can contact their biological father at 18 if they wish. From hundreds of possible donors, Geoff chose one "who is remarkably like me - he rides bikes, he listens to music, his lineage is Anglo-Scottish." The couple are currently having fertility treatment in Bristol using this donated sperm.

The HFEA hope that such a system will eventually be available in Britain - that men and women will come forward to donate their sperm and eggs out of altruism, happy in the knowledge that they may one day meet their offspring. In the meantime, infertile couples will face very difficult choices about how far - both geographically and morally - they are prepared to go.

Some of the names have been changed