You shouldn't have to tell him anything, if he's a grown man he will will know how the world works. If you have sex then women can get pregnant. If you absolutely do not want to have a baby then you take personal responsibility to ensure it doesn't happen.I find it very sad that I have to tell my son to always wear a condom because he can’t completely believe any woman he sleeps with, even if he’s in a long term relationship, you would think a long term partner could be trusted but as this thread shows you shouldn’t