It does not. You're confusing the difference between something not being as effective at avoiding pregnancy with something that causes pregnancy.
Really, you believe that?
Deuce said, "Leads to"....and that's a very significant part of what he said.
Abstinence is 100% effective. Not quite as effective...or leads to being a little more effective. It's 100% effective. Problem is lusty, horney hormones whispers, excuse me, screams in kids ears. And kids are loaded with them.
So what do you suppose that an abstinence program would actually teach kids about sex itself, who will absolutely not abstain, no matter how many times they hear..."Just say no to sex, it'll ruin your life, and you'll get nasty diseases!"
The topic should be: WHEN YOU HAVE SEX!...yadda, yadda, yadda.
Not having sex...there's something amuck. But the good news is that kids who are getting the straight story, they have used that information wisely, and over the last 10 or so years teen pregnancies have gone down by about 40%...just by telling them the truth about sex and how to engage in safe sex. This means that they've actually been using birth control more and more. They probably get their birth control from Planned Parenthood...you know the evil place that prevents more abortions than they perform...and probably by a long shot. And boys and girls get the STD stuff. The boy wear condoms. They have female condoms, too.
Some of us are just plain old human beings. In fact, if you look around the planet you'll see about 7 plus billion plain old human beings. 7 billion people didn't get beamed down by Scotty. Sooner or later we all are going to have sex. I'm betting you did too. And I bet you didn't attend an abstinence only program.