WASHINGTON (AP) -- A judge on Wednesday denied an advocacy group's bid to prevent the government from giving pregnant women flu vaccines with a preservative that contains mercury.

Leaders of the Coalition for Mercury-Free Drugs say their effort took on a new urgency when a government advisory committee recently recommended that pregnant women be among the first people to get swine flu vaccinations when the vaccine becomes available this fall.

A small amount of the mercury-containing preservative thimerosal is in most influenza shots, including swine flu vaccines, but some are produced thimerosal-free. The coalition argued that pregnant women should only get the thimerosal-free version because of a risk that the mercury in the shot could poison a fetus and cause medical problems, including autism.

But U.S. District Judge Reggie Walton ruled against the group's request for a preliminary injunction because he said the group couldn't prove that pregnant women they represent would get vaccines containing thimerosal.

Walton said he would consider further written arguments in the next month about whether the lawsuit can continue.

Thimerosal used to be used in a number of vaccines, but manufacturers began removing the preservative from all routine child vaccines in 2001 as a precaution. But numerous large studies have shown no link between thimerosal and autism, or other health problems.

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