“I like children but I don’t dare to have them here because I won’t be able to protect them,” she said, citing concerns like pandemic control workers breaking into apartments to spray disinfectant, killing pets and requiring residents to leave the keys in their apartment door locks.

Ms. Cheng is part of a new trend known as the “run philosophy,” or “runxue,” that preaches running away from China to seek a safer and brighter future. She and millions of others also reposted a video in which a young man pushed back against police officers who warned that his family would be punished for three generations if he refused to go to a quarantine camp. “This will be our last generation,” he told the police.

His response became an online meme that was later censored. Many young people identified with the sentiment, saying they would be reluctant to have children under the increasingly authoritarian government.

“Not bringing children to this country, to this land, will be the most charitable deed I could manage,” wrote a Weibo user under the hashtag #thelastgeneration before it was censored. “As ordinary people who’re not entitled to individual dignity, our reproductive organs will be our last resort,” wrote another Weibo user.