By Emma Wilkinson
BBC News health reporter in Amsterdam
Many women are travelling abroad to have a family
Hundreds of British couples travel to the continent every month for fertility treatment because they cannot get it at home, a Europe-wide study suggests.
Almost two-thirds of those taking part in a snapshot analysis were over 40 years old and unlikely to be eligible for IVF on the NHS.
The researchers said lack of egg donation was also prompting UK couples to seek treatment abroad.
The researchers examined patients at clinics in six European countries.
They were in Belgium, the Czech Republic, Denmark, Slovenia, Spain and Switzerland.
In one month, a taskforce from the European Society of Human Reproduction and Embryology (ESHRE) gathered data from 1,230 patients - 53 of whom were British.
Most patients in the survey were originally from Italy, Germany, the Netherlands and France.
Spain and the Czech Republic were the most common destinations for British patients which the researchers said was probably due to easier access to egg donation.
When asked why they had travelled abroad, 34% of British patients cited problems with access to fertility treatment at home - more than any other nationality.
Overall British women were older than those from other countries, the oldest being 49.
The main reason given by women from Germany, Norway, Italy and France for seeking treatment in another country was to avoid legal restrictions at home.
The figures are the first hard evidence of considerable fertility tourism in Europe, the researchers said.
In May, a businesswoman became Britain's oldest mother at 66 after undergoing fertility treatment in the Ukraine.
Elizabeth Adeney, who is not the first women in her 60s to conceive after IVF, gave birth to a baby boy in Cambridge.
But study leader Dr Francoise Shenfield from University College Hospital in London said such cases were rare and 50 should be the cut off for treatment with an egg donor.
She said the figures suggested hundreds of British women were visiting foreign clinics.
"Access is a big reason for women from the UK.
"It's very difficult for us to get funding for patients over the age of 39.
"When they're 39 or 40 they're stuck. Britain is bad at access.
"We know that 75% of IVF cycles in the UK are still carried out in the private sector."
The shortage of donated eggs in the UK was also a factor, she said.
Changes to anonymity rules in 2005 which meant British donors could be identified as the biological mother or father of an IVF child has deterred people from donating.
Other barriers to NHS treatment include being obese, she added.
Speaking at the ESHRE annual meeting, she said cross-border treatment for these "extremely motivated" patients should not be restricted but women needed to have information on treatments in other countries to make sure they were safe.
One worry is that women travelling abroad may be more likely to have two or three embryos put back increasing their chances of twins and triplets and putting them at risk of complications.
Professor Basil Tarlatzis, president of the International Federation of Fertility Societies, said: "Of course each country has the right to set its own standards of fertility treatments.
Having said that, we believe that it's a fundamental freedom that people should have access to medical treatment, and if they need to travel to do that, then that's fine.
"We need to make sure that standards are maintained, and that the results of these visits are available for evaluation."
Clare Lewis-Jones, of the Infertility Network UK said "If patients could access treatment in the UK many would not be forced to consider going abroad.
"It is absolutely vital that anyone considering travelling abroad should do some thorough research beforehand as the rules and regulations abroad can be totally different from that in the UK."