Do you think that people don't already know what sex causes? Yet they defy the odds and suffer the consequences anyway. It occurs to me that the consequences are the result of the actions. You can solve the problem by ameliorating the consequences, or you can eliminate the actions.
You have resigned yourself to the impossibility of halting the action, so you focus instead on minimizing the consequences. I would prefer that our society put more emphasis on stopping the problem at its source, by instilling in these teenagers a sense of morality that is not belied by slick commercials, corrupt (or absent) role models, and institutionalized hypocrisy.
Did teenagers in the old days abstain solely out of a sense of morality, or fear of unwed pregnancy? That fear has declined because of contraception and the fading of the stigma against illegimacy. Informing kids about STDs and prevention (including the fact that some STDs have be transmitted even with the use of a condom) would perhaps encourage more teens to abstain or at least delay sexual activity.