[Irravepem]

Here we go, the facts I know:

[...]Three small studies found no motile sperm (sperm capable of reaching/fertilizing an egg) in the fluid in a man’s penis before he ejaculates. [...]

http://ec.princeton.edu/questions/preejac.html

It's no 'common misconception', Steve. Again, these are small studies, but I wouldn't break a sweat about it. The transfer of STDs is far more likely, though.