Maury Rule

The rule to only have sex with one guy per menstruation cycle. That way, if you get pregnant you won't end up on "The Maury Show" trying to figure out which one is the father?

Girl 1: I'm sorry Tony dumped you, but that Mark is looking fine! Are you gonna let him ..."comfort you" this weekend?

Girl 2: No girl, I'm obeying the "Maury Rule"... if I get pregnant, I'm going to know EXACTLY who the daddy is. Mark and I can wait a few weeks.