'A promiscuous she-pope with a dilated cervix': the legend of Pope Joan, who gave birth on a horse
If Pope Joan — the infamous female pope of the 9th century – didn’t exist, you can see why someone would have had to invent her. For the Catholic Church, she became a story of why women should not be allowed to hold power; for the Protestants, she was a helpful argument against falsehoods embedded in the papacy. A woman who inveigled her way onto St Peter’s throne, some said the “Popess” was English; others German. A popular medieval version of her tale has her gender “discovered” during a papal procession because she gives birth while trying to mount her horse.
Source: theconversation.com