WASHINGTON — There was a striking island of white in the audience for President Trump’s State of the Union address, with House Democratic women — many of them dressed in the color in a nod to the American suffragist movement — sitting together in the packed chamber, in a celebration of their historic numbers in Congress and also as a protest to Mr. Trump’s policies.

Midway through the president’s speech, they did something completely unexpected: They stood up and cheered for something Mr. Trump had said.

“No one has benefited more from our thriving economy than women, who have filled 58 percent of the newly created jobs last year,” Mr. Trump told the nation, prompting the women to rise from their seats, pointing at themselves and nearly dancing.

The president was taken aback. “You weren’t supposed to do that,” he said, pleased.

“All Americans can be proud that we have more women in the work force than ever before,” Mr. Trump went on. He paused for a moment and added, “Don’t sit yet, you’re going to like this.”

And then he delivered his biggest applause line, one that brought Speaker Nancy Pelosi to her feet: “And exactly one century after Congress passed the constitutional amendment giving women the right to vote, we also have more women serving in Congress than at any time before.”

Ms. Pelosi stood up and stretched her arms toward the audience, as they cheered again in celebration of the record 131 women who now serve in the House and the Senate. They gave one another high-fives and joined in as the chamber erupted into chants of “U.S.A.! U.S.A.!” — more common at Trump rallies than at a formal address in the Capitol.

“That’s great,” the president said, seeming to address the women. He ad-libbed, smiling, “Congratulations.”

It was a striking moment for a president who has been routinely accused of misogyny, who is implicated in a scheme to pay hush money to a pornographic film actress and a Playboy model and who was caught on tape boasting about grabbing women’s genitals.

Perhaps no group has been more critical of Mr. Trump than Democratic women — especially the vocal House Democratic freshmen, many of them first-time candidates who marched in Washington the day after Mr. Trump’s inauguration, and who were motivated to run for office to thwart his policies.

Before the speech, many Democratic women said they felt moved to wear white in a visual protest of the Trump administration’s policies affecting women, from health care and reproductive rights to equal pay. They felt especially determined after the White House said he would talk about abortion during his speech.

“I’m sure you know we’re all wearing suffragette white as women,” Representative Pramila Jayapal, Democrat of Washington and a chairwoman of the Congressional Progressive Caucus, told reporters in a conference call on Monday.

She added, “I think the goal here is to really show the tremendous step backward that our country has taken under this president and to call out the very specific ways in which he has pushed policies to undermine our climate, undermine immigrants, undermine worker protections and undermine of course women’s reproductive rights.”