By Angus Roxburgh
BBC News Online
Thousands of women across Europe conceive babies by artificial insemination every year.
But changes in the law in several countries, removing the right of sperm donors to remain anonymous, have caused a dramatic drop in the number of men willing to donate.
This could severely undermine the whole idea of artificial insemination as a solution for infertility, or for women who wish to have children without having a husband.
Some Dutch women are travelling to Belgium for IVF treatment
The Netherlands abolished donor anonymity in June, Sweden did so earlier, and the UK will follow suit next May. The reason for the change is to give children conceived by sperm donation the right to know the identity of their biological fathers.
But one Dutch sperm bank, in the town of Maastricht, has had no new sperm donors for six months, and its chief, Dr Gerard Dunselman, fears he may have to close down the facility altogether.
He himself supports the new law, but admits it has had a catastrophic effect on his work. He has no option but to advise women to cross the border to Belgium, where sperm donors remain anonymous and there is no shortage.
Just across the border in the town of Genk, the artificial insemination clinic run by Dr Willem Ombelet has seen business soar.
"We used to see two to three women a month, now it's two to three a week," he says.
His clinic uses sperm that is from Belgian donors or imported from Denmark.
But is not because Dutch women are determined that the fathers of their children should remain anonymous that they are coming to Belgium, Dr Ombelet says.
"Parents don't care about anonymity, it's simply because of the long waiting lists in Holland."
Martha Roegholt, in the Dutch village of Baambrugge, had two babies by artificial insemination, and has now written a book about the moral, psychological and social issues surrounding it.
She says that under the old Dutch system, donors could choose to be anonymous or known, and a woman could choose which type of donor to use.
Children conceived by anonymous donor were given only basic information about the father - his race, age, colouring, profession - and Ms Roegholt believes most children were satisfied with such details.
But her daughter Rian, now aged 19, is disappointed that she will never be able to trace her father. She has dark eyes and complexion, and wonders whether her father might have been Spanish.
"It's not something I think about constantly," she says. "I'm just curious. It would be nice to meet him."
It is to meet the wishes of such children that the law has now been changed. When they reach the age of 16, children conceived by artificial insemination will have the right to trace their biological fathers.
The right does not apply retrospectively to those conceived under the old system.
Rian says she is curious about her donor father
The experience in Sweden, the Netherlands and Britain in advance of the introduction of the new law is that most donors are unwilling to face this prospect.
Peter, a regular donor at a sperm bank in Brussels, says he would stop immediately if the law changed in Belgium.
"I do this because I want to help people who cannot have children. I don't know how many children I have fathered, and don't want to know. The right of the child is all very well, but so is the right of the donor - and without donors you don't have children."
Numbers of sperm donors in Sweden have recovered somewhat since the initial collapse, but there is little doubt that giving children the right to know the identity of their fathers makes the whole practice of artificial insemination less viable.
Dutch women can go to nearby Belgium for anonymous treatment, but travelling abroad will be a much more expensive option for British women when the law changes there.
Nor will it be possible for British women to import sperm from countries like Denmark or Belgium, where donors are anonymous, because under the new law children must have the right to trace their fathers.
The danger is that women seeking treatment will turn to less trustworthy, less regulated sources, such as the internet, and that artificial insemination becomes a semi-legal activity.
"Our clinic carries out rigorous tests on the donors and their sperm," says Professor Herman Tournaye of the Brussels sperm bank.
"We test for genetic problems and compatibility with the mother, and keep sperm for six months before using it in case the donor develops a transmittable disease in the meantime. If you buy sperm on the internet, you cannot be sure that the same care is taken."