U.S. sperm banks are running low on donor sperm that can produce blond, blue-eyed Scandinavian babies, the result of a 2005 U.S. Food and Drug Administration ban on sperm from any European countries with exposure to mad cow disease.

The move effectively eliminated donors from Denmark to the United Kingdom.

While some U.S. sperm banks have had enough frozen stocks to cope with the demand, they are now running low.

"We still have a little bit left, but not much," said Claus Rodgaard, manager of Cryos International, a Danish-based sperm bank with an office in New York.

"We're not here to promote people to have blond, blue-eyed babies, but if those are the kinds of characteristics you're looking for, then Danish sperm is good for that," Rodgaard said. "That's all we have in Denmark."

Scientists say the ban is not justified.

"The consensus in the United Kingdom is that this is a silly ban," said Dr. Allan Pacey, an andrology expert at the University of Sheffield and secretary of the British Fertility Society. "There's no evidence to show that mad cow disease can be transmitted in human semen."

The human form of mad cow disease, Creutzfeldt-Jakob disease, is mainly transmitted after people eat meat infected with bovine spongiform encephalopathy, or BSE. In rare cases, the disease has also been spread by contaminated surgical equipment or in transplants of brain tissue.

There has never been a documented case ofCreutzfeldt-Jakob being passed on after a sperm donation.

Pacey said concerned doctors could always screen potential donors to see if they might be at high risk for mad cow disease, but that a blanket ban was unnecessary.

Canada does not ban the importation of semen from any country, but any semen imported into the country is strictly regulated under the Food and Drugs Act and the Assisted Human Reproduction Act, Carole Saindon, a spokesman for Health Canada, told the Canadian Press in an e-mail.

"The Semen Regulations, under the Food and Drugs Act, specify strict requirements for the screening of donors for infectious diseases and for other factors or behaviours that could increase the risk of an infectious disease being present," Saindon wrote. "The regulations further state that any imported semen must be accompanied by documentation showing that it is in compliance with the Canadian regulations."