I read on one of those "Yahoo Answers" pages when looking up my cliche, and the arbest thing i had read among all the answers was this story this women had written in...
And it goes like this:
"My Stepmother is part Native American and she had said that in her culture, when a child is crossing their fingers it is a 'sign' that somebody in the family is pregnant."
Later on in the same post this woman then wrote that her 2 year old son had been crossing his fingers and she had later discovered she was pregnant with her 2nd child... It isn't for everyone to believe, but it apparently does work?