Historically, it was common for American teachers to be pushed out of their jobs during pregnancy, either through termination or the requirement of an unpaid leave of absence.

In 1974, the Supreme Court ruled some of these policies unconstitutional. But not all such policies were explicitly written down and tracked, giving many female teachers little legal recourse.

CBS News quoted a retired teacher from Ms. Warren’s school, Trudy Randall, who suggested Ms. Warren would have been unwelcome at the school given her pregnancy.

“The rule was at five months you had to leave when you were pregnant. Now, if you didn’t tell anybody you were pregnant, and they didn’t know, you could fudge it and try to stay on a little bit longer,” Ms. Randall was quoted as saying. “But they kind of wanted you out if you were pregnant.”

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At issue are the circumstances that brought to an end Ms. Warren’s brief career as a special needs teacher at an elementary school in Riverdale, N.J., where she worked from 1970 to 1971, when she was just out of college. On the campaign trail, Ms. Warren’s personal story is a central part of her stump speech, beginning with her upbringing in Oklahoma and, eventually, her experience as a teacher. As Ms. Warren tells it, she had wanted to be a teacher since she was in second grade.

“I loved that work, and I would probably still be doing that work today, but my story has some more turns,” she told a crowd in Nevada last week. “By the end of the first year, I was visibly pregnant, and the principal did what principals did in those days: wished me luck and hired someone else for the job.”

She included a similar account in her 2014 memoir. In some retellings earlier this year, she said the principal “showed me the door.”