How do you talk to your son about premarital ?

My wife wants me to talk to my son about premarital , basically not to have it and wait until he is married. The only thing is that I have never lied to my son before and although my wife waited for marriage, I most certainly did not. I don't want to start lying to my son now and say something that I don't truly believe in but at the same time, as a parent, I obviously see where my wife is coming from. Does anyone have suggestions as to what to do?