Michelle Obama issued an impassioned plea to American voters on Saturday — and, in particular, American men — anchored in a searing and intimate depiction of women’s bodies and reproductive health, and what she described as the life-or-death stakes of returning former President Donald J. Trump to power.

In her first appearance on the campaign trail during this election, Mrs. Obama, long reluctant to engage in the political arena, described the far-reaching consequences of the 2022 Supreme Court decision overturning the constitutional right to abortion, in the concrete terms of personal tragedy.

“If your wife is shivering and bleeding on the operating room table during a routine delivery gone bad, her pressure dropping as she loses more and more blood, or some unforeseen infection spreads and her doctors aren’t sure if they can act, you will be the one praying that it’s not too late,” Mrs. Obama said. “You will be the one pleading for somebody, anybody, to do something.”

And while she acknowledged the anger that many Americans feel about the “slow pace of change” in the country, she warned: “If we don’t get this election right, your wife, your daughter, your mother, we as women, will become collateral damage to your rage.”

Mrs. Obama’s words — at a rally in Michigan where she introduced Vice President Kamala Harris — amounted to an extraordinary centering of women’s bodies and their private experiences in an American presidential election. She discussed menstrual cramps and hot flashes, describing the shame and uncertainty girls and women feel about their bodies. She told women they should demand to be treated as more than “baby-making vessels.”