The notices, posted on the Shenzhen, Hunan and Qinghai state-backed unions' official Wechat pages in the past week, were among the most widely circulated items on social media on Monday, with many netizens saying it was a step in the right direction to address widespread gender inequality.
It has become increasingly common in China for companies to quiz female job seekers about their marriage or child-bearing plans during job interviews.
Fear of having to give up their career or be sidelined if they start a family has been a growing concern for many young Chinese women who opt not to give birth as a result.
Chinese authorities, worried about the country's declining population growth, have pledged a series of measures to try to incentivise births, including subsidies, but have not successfully addressed entrenched gender stereotypes where women are seen as the chief caregivers.
During recruitment, employers should not give priority to men, the notice from the Hunan Federation of Trade Unions said.
"Employers shall not further inquire or investigate the marital and child-bearing status of female job seekers", while contracts should "not stipulate restrictions on marriage and child-bearing of female employees", it said.
Female employees could not be dismissed or see their salaries cut due to marriage, pregnancy, childbirth or breastfeeding, it said.
Many netizens welcomed the move while some were sceptical and said it might make employers stop hiring women altogether.
"Discrimination still exists and they will still refuse to hire you because of concerns about your marriage and child-bearing," one netizen said.
Another pointed out the societal ironies.
"In the workplace, women are required not to have children but society requires women to have more children. After having children, women are required to take care of children and the family while earning money in society. Isn't this contradictory?"
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