I am not an expert but I heard once that....
Male (Boy) sperm are faster than Female (girly) sperm... which has something to do with what you will have...
If you are ovulating and all that (whatever the technical term

) when you do your
business then the boy sperm get first crack

, but if your bits haven't started to be ready for the little wigglers.. (whatever the technical term is

) then the
Boy sperm go on their merry way with nothing to crack open while the
Girly sperm are still traveling along... (
for up to four days) and then they WIN and get the egg when it comes along because they hadn't died off yet... or something like that... :shrugs:
Sorry, never really took the sex ed class or have had the ability to speak in adult terms on the subject...

Not really a myth as much as it is a science that I have butchered with my explanation...