Three Supreme Court justices voiced doubts Wednesday about the wisdom or legality of an employer's "fetal protection" policy that excludes all women of childbearing age from some hazardous jobs.

In a case that could affect millions of working women, Justices John Paul Stevens, Antonin Scalia and Sandra Day O'Connor posed questions seemingly critical of the policy during an hourlong argument session.Stevens questioned Stanley Jaspan, a lawyer for the Milwaukee-based Johnson Controls Inc., about the risks to women working in its battery-making factories.

"Is the slightest risk enough" to justify banning women from some jobs, Stevens asked.

O'Connor and Scalia took issue with Jaspan's interpretation of what burdens Congress placed on employers when it passed the Pregnancy Discrimination Act in 1978.

Scalia told Jaspan his suggestion that the 1978 law means employers cannot discriminate against women based on pregnancy except to protect a fetus "is to make a farce of the Pregnancy Discrimination Act. You're making it a ridiculous piece of legislation."

Since 1982, Johnson Controls, the nation's largest auto battery manufacturer, has barred women from factory jobs that expose them to unsafe levels of lead, the principal material used in making batteries.

The policy was upheld by lower courts.

Lead exposure is a health risk for female workers and their fetuses.

"It would violate common sense . . . to require an employer to damage unborn children," Jaspan argued.

The justices must decide by July whether the fetal protection policy amounts to illegal discrimination.