When the British American writer Ruth Whippman decided to thaw one final embryo, she was 42 years old. She and her husband had two sons, Solly, then 6, and Zephy, 3. Their remaining embryos all had XY chromosomes, too.

As her pregnancy became visible, most people assumed she was trying for a girl. When she told them she was having a boy, people treated her “as this object of pity,” Ms. Whippman said in a recent interview from her home in Berkeley, Calif. “There was this real sense that boys were somehow disappointing.”

Even her mail carrier expressed her sympathy.

It was 2017. Ms. Whippman, a self-described liberal feminist, was watching the #MeToo movement explode all around her. She felt as though men had become the enemy, which made bringing another one into the world a different kind of challenge from what she already faced at home with two rambunctious little boys.

But she was conflicted. “While the feminist part of me yelled, ‘Smash the patriarchy!’ the mother part of me wanted to wrap the patriarchy up in its blankie and read it a story,” she writes in her new book, “BoyMom,” out this week.

The title of the book borrows from the social media phenomenon known as #BoyMom, a hashtag that has become a full-blown trend in recent months and has as many interpretations as a Rorschach test.

Online, #BoyMom can be a badge of honor awarded for simply surviving the amped-up hi-jinx of tumbling boy-tots; or it can be a tragedy, centering on the inevitable “break up” that must occur between mothers and son; or it can it be a sendup of itself, a parody of the “toxic boy mom” who is dangerously, proudly enmeshed with her son.