From Disney, 1946. A basic explanation of the purpose and process of menstruation, told largely with diagrams (and completely avoiding the subject of sex).
It was co-produced with Kotex to teach pre-teen girls about Menstruation, supposably. It only educates at a superficial level, so it does not go into heavy detail for the animated "Ram's Head"/ Reproductive System sequence.
The Story of Menstruation is believed to be the first film to use the word vagina in its screenplay.