Yes, thank you, menstruation isn't usually taken to be a key factor here, but now I'm thinking about it—because menstruation is real important in the Bible.

Two Hebrew words are used for young women: betulah and almah.

In Gen 24:16, Rebecca is a "betulah…whom no man has known." In Gen 24:43, Rebecca is called an "almah." This word has a masculine form, elem, but betulah doesn't have a masculine form.

The usual distinction made by readers is that betulah is "virgin" and almah is "young woman." But as I think about your comment, I believe that betulah more likely means "menstruant."

But almah seems to mean "young woman" without much scrutiny of her reproductive situation.