No Man of Her Own (1950) on Netflix

Plot summary

Helen Ferguson is unmarried, eight months pregnant and broke in New York. She goes to the apartment of her unfaithful boyfriend Stephen Morley and pleads for help through the door; he refuses to answer, but slides an envelope out to her holding a five-dollar bill and a ticket to San Francisco. With nothing else open to her, she takes the train. The journey ends in a crash, and in the wreckage the authorities mistake Helen for Patrice Harkness, another pregnant passenger, whose husband Hugh was killed as well. Helen gives birth to her child in a hospital, and the Harkness family, who never saw their son's wife, accept her as Patrice. The family reads her confusion and lapses of memory as aftereffects of the wreck, and for her baby's sake Helen does not correct them.