Political advocacy ads that ran earlier this week in a number of swing states featured a sonogram of a fetus, but they had nothing to do with abortion.

Rather, the television spots, underwritten by the Environmental Defense Fund, told voters that their Representative had voted for a measure that could increase the danger of mercury poisoning to pregnant women.

It is part of the latest campaign by environmentalists to grab the public’s attention to head off what they see as overly broad efforts by Republicans to weaken or eliminate a slew of air and water pollution rules.

“We are staring down the barrel of the 112th Congress and facing a mostly defensive agenda,” said Melinda Pierce, legislative director of the Sierra Club.

Both as part of the budget and stand-alone bills, House Republicans are pushing legislation that would undo much of the environmental agenda being promulgated by the Obama administration.

The House Energy and Commerce Committee is expected to soon take up a measure that would block the Environmental Protection Agency from issuing greenhouse gas emission standards. The continuing resolution approved last month by the House included amendments that would curb funding for a range of EPA activities, including rules restricting mercury releases from cement kilns.

The environmental groups are banking that the Democratic-controlled Senate will not allow many of the amendments included in the House budget bill. Nevertheless, many of these activists were stunned at the number of provisions that were approved by the House that, among other things, prohibited the government from regulating water pollution discharges into the Chesapeake Bay, enforcing mining restrictions in Appalachia and setting up fishing management programs off the coast of New England.

Tony Kreindler, a spokesman for the Environmental Defense Fund, said his group was involved in “hand-to-hand combat on the budget.”

Republicans have argued that these environmental restrictions were overly burdensome to businesses and cost jobs.

But to convince voters that eliminating these regulations have a direct effect on their lives, the EDF and another environmental group, the League of Conservation Voters, decided to highlight the mercury emissions issue.

The amendment, sponsored by Reps. John Carter (R-Texas) and Mike Ross (D-Ark.), would prevent the EPA from proceeding with new rules aimed at eliminating 92 percent of mercury and fine-particle emissions from cement kilns.

The amendment was supported by the Portland Cement Association, which represents many of the kilns. It claimed the regulations would force the industry to shut down 18 plants, comprising 11 percent of its production.

But environmentalists said that mercury poisoning is of concern to Americans because of its effect on pregnant women and children.

“The mercury vote exemplified how extreme this Congress will be,” said Navin Nayak, director of global warming programs at the League of Conservation Voters.

The league recently ran $100,000 worth of radio spots in key Congressional districts telling voters that their Member had voted “to block enforcement of a vital mercury pollution law.”

The spots ran in the districts of Democratic Rep. Jason Altmire (Pa.) and GOP Reps. Tim Walberg (Mich.), Denny Rehberg (Mont.), Lou Barletta (Pa.) and Fred Upton (Mich.), who is chairman of the Energy and Commerce Committee. Nayak said the group largely focused on districts that President Barack Obama won in 2008. The EDF ran its television ads on the mercury amendment that included the sonogram image in a number of markets that covered swing Congressional districts in suburban Philadelphia, New England, Ohio and Montana. It ran during programming often watched by women, including “Ellen,” “Oprah” and “The View.”

The Sierra Club, meanwhile, has been focused on the southwest Michigan district represented by Upton, holding events in Kalamazoo and running ads in the district.

“This is the new hot spot in our nation’s political map,” Pierce said.

While Pierce said Upton had a reputation as a moderate, he has lately followed the lead of the House Republican leadership regarding environmental regulations.

The conflict over environmental regulations was on display Tuesday in a House Energy and Commerce subcommittee, which heard testimony from a panel of scientists over the validity of global warming research.

The hearing was held at the insistence of Rep. Henry Waxman (D-Calif.), the ranking member of the Energy and Commerce Committee who was sharply critical of legislation that would bar the EPA from regulating greenhouse gases. The measure is sponsored by Upton and Sen. James Inhofe (Okla.), the top Republican on the Senate Environment and Public Works Committee and a vocal critic of global warming.

The Democrats brought their props, piling up a stack of studies supporting the science behind climate change. And they sent a message to Upton by inviting Knute Nadelhoffer, a professor of ecology and evolutionary biology at the University of Michigan, who spoke of the deleterious effect of warming trends on the Great Lakes.

But the chairman of the subcommittee, Ed Whitfield (R-Ky.), held up his own study on global warming and said that the EPA’s regulations would not solve the problem.

“There’s no question EPA’s rules are bad economic policy, but they may very well be bad environmental policy,” he said.