For Vietnam’s legion of factory workers, the mathematics of making a living was complicated enough before President Trump announced a whopping tariff on the goods they make.

Nguyen Thi Tuyet Hanh worked two factory jobs, six days a week, for nearly a year after her husband lost his job in 2023. She had no other choice to help feed their four children and keep them in school.

“It was brutal,” Ms. Hanh, 40, said. Her husband is working full time again at a factory, but Mr. Trump’s plan to put a 46 percent tariff on imports from Vietnam hangs over their family, which lives in a row of concrete tenements on the outskirts of Ho Chi Minh City.

“My family lived through that difficult time — I don’t want to live it again,” said Ms. Hanh, who earns $577 a month as a line manager overseeing 138 workers making shoes for Nike, the French sporting goods company Salomon and other global brands.

Fear is reverberating on her factory floor, alive with the hum of sewing machines stitching the fabric for shoes that are shipped to the United States. Mr. Trump paused the tariff on Vietnam, and similar levies on dozens of other countries, for 90 days. But it hardly matters here. The destabilizing prospect that the tariffs will be reinstated is already chipping away at Vietnam’s economic growth, which hinges on making things for American consumers.