Responding to some earlier posts, I'll point out that Marie-Lynn Hammond has in fact written and recorded "Period Piece (The Rag Song)", which is about menstruation. It's on her CD "Impromptu", and she's posted the full lyrics here. Here's a brief excerpt:

...now some clever soul's discovered yet another problem
though some think that to discuss it is in quite poor taste

But that has never stopped me in the past so I will tell you
that it has to do with women and our physiology
and those tampons, pads, and plastic applicators that are
monthly blocking sewers, clogging landfills and polluting the sea...