Well, of course not. But tell that to the thousands of people that wind of pregnant from either carelessness, ignorance or defiance. Sex happens, and obviously people do not think about a fetus when they are in the throws of passion.
So, can you stop sex? No you can't. Can you support organizations that are in the business to teach about birth control? Yes you can.
The Cause is sex. The answer is supporting birth control education.
Which is cheaper? About the same price if you add up all those birth control pills. Which is sadder? Abortion is, of course.