Peter Stanford's work, The She-Pope, is apparently being turned into a film. The basic gist of the work is that one woman managed to become pope, only to give birth to a child in public (thereby betraying her secret). Allegedly this all took place in the late 9th century. The story should be taken with a whole shaker of salt, for a variety of reasons. Nevertheless, it is an interesting story with more and better factual support than, say, the alleged bodily assumption of Mary.
(Link to article: CAUTION - web page features immodest women, and story is a little explicit about how the Church allegedly avoids another Pope Joan. Thus, this link is neither for those with lust problems, or for children.)