Talking of unscientific theories, growing up I always thought that men with facial hair will have girls - this was based on - an uncle having three girls, my friend being one of two girls and her dad had a mustache and Kevin Webster from Coronation Street having two girls. :-)

Of course who knows whether any of these had facial hair at time of conception.

Maybe now with Movember being around someone could see whether there are more girls born 9 months after November than in other months :-)