WASHINGTON — The Supreme Court on Wednesday weighed how much protection Congress meant to give pregnant workers when they ask for a change in their usual duties because of their condition.

The court tread somewhat gingerly through an hour of technical arguments in the case of Peggy Young of Lorton, Virginia, a former driver for United Parcel Service. She charges that the company violated federal law when it refused to temporarily change her duties after a doctor suggested that she not lift heavy packages. Young was forced to take unpaid leave, and she says the company denied her accommodations that non-pregnant workers receive.

The case presents the court with questions about a changing American workplace and how far government and private businesses must go to accommodate the needs of an increasing number of women who work through their pregnancies and serve as the breadwinners for their families.

For the most part, those issues took a back seat to detailed questions about punctuation and ambiguous language in the Pregnancy Discrimination Act of 1978.

But the nature of the discussion changed during a colloquy between Justice Elena Kagan and Caitlin Halligan, the New York lawyer representing UPS. Near the end of her turn at the podium, where she was peppered with dozens of questions from Kagan and Justice Ruth Bader Ginsburg, Halligan said the act “sets a floor. That floor is that you can’t single out pregnancy for adverse treatment.”

Beyond that, she said, the democratic process should take hold and states can add additional protection as they see fit, as nine states, including Maryland, already have done.

“Well, Ms. Halligan, for the democratic process to work as it should, the PDA has to be given a fair reading,” Kagan responded. “And what we know about the PDA is that it was supposed to be about removing stereotypes of pregnant women as marginal workers. And what you are saying is that there’s a policy that accommodates some workers, but puts all pregnant women on one side of the line.”

It was unclear from the court’s questioning exactly how the case would come out. Kagan seemed to be searching for some middle ground that would allow Young to continue her lawsuit with specific allegations about the company’s different treatment of workers and allow the company to justify why the workers are treated differently.

Young filed the suit in federal district court in Maryland in 2009 and still has not received a trial. The district court granted summary judgment for UPS, and the U.S. Court of Appeals for the 4th Circuit affirmed that decision.

Except for the extended and at times animated back-and-forth between Kagan and Halligan, the questioning was subdued, especially from the conservative male justices who have ruled against women’s rights groups recently in cases involving workplace discrimination and contraceptives. Chief Justice John Roberts Jr. made only brief comments, and Justice Anthony Kennedy’s questions were few. Justices Antonin Scalia and Samuel Alito Jr. seemed skeptical that the 1978 act offered all the protection Young claimed.