It only takes having sex once to get pregnant. If if you have never had vaginal sex before, you can still get pregnant the first time you do. All you need is for the woman to be ovulating and for one sperm to meet up with it. In one seminal emission from a man there are tons of sperm. And yes, even pre-ejaculation has sperm in it, which is why the pull-out method does not work very well at preventing pregnancy.
