Personally, I think getting pregnant as a teenager is a bad idea. But I'm not so arrogant as to presume that my ideal life plan is right for everyone. And rather than consider "teen pregnancy" this big, social evil, it bears recognizing that thousands of years of evolution are backing a teen's strong desire to get laid. In today's rational, civilized world, the ideal conditions for parenthood have perhaps changed, but if we want to fight this overpowering biological impulse, we should first acknowledge its strength, and refrain from treating those who fail to resist it as lesser beings.
Now, certainly, unplanned pregnancy is quite a problem. More so than it would have been in prehistoric days, when pretty much the sole drive in life was to procreate. But I don't think discouraging teens from having sex is nearly as effective as teaching them how to do it safely. Unfortunately, some people are just too stupid to prevent getting pregnant unexpectedly, or too stubborn to understand why they probably shouldn't get pregnant when they still live with their parents, are legal minors, and haven't even graduated from high school. I don't know what we can do about them - possibly nothing, as again, you have to recognize the overpowering biological impulse behind these modern social snafus.
But the term "teen pregnancy" - as a thing that ought to be prevented - is kind of a little offensive. Like, it implies that there are no conditions under which a teen getting pregnant is a) a good thing, and b) the right decision for that teen. 18 and 19 year olds are teens, too, and they are old enough to be out of high school. And though we encourage all kids to go to college if they can afford it (many can't), for some people, starting life at 18 is the right thing to do (and waiting only makes things worse).
Consider, for example, the 16 year old girl who starts dating a man a few years older than her (because women mature faster than men, and because while women are traditionally given the role of mother and homemaker, the man is expected to provide for the family, which in modern days means getting a well-paying job - something a college graduate is probably more likely to have than a high school graduate). In a couple years, she graduates high school, and her boyfriend graduates college. He gets a great job with good prospects right out of college, and the girl is ready to start a family. They've been going out for at least two years now, are compatible, and really like each other. So they get married, and conceive their first child. The girl is 18. Is her pregnancy one of the ones that the Society for the Prevention of Teen and Unplanned Pregnancy is trying to prevent?
I get that "preventing unplanned pregnancy" doesn't accurately address the problem of teens getting pregnant willfully when they probably shouldn't. And I think it's important to get through to those who really haven't thought it through, and don't have the means to support a child, before they make that decision (although for those who have, I'll respect their decision, whether I agree with it or not). But the whole paradigm of "teen pregnancy is bad" seems to support this underlying belief that teens are inadequately prepared to make responsible decisions about their own sex lives. And while many of them may be, in a lot of cases the solution is better education, and certainly, it's not the case with every single teen. And, ultimately, it just supports the agenda of trying to keep teens from having sex ("wait until you're older" is their mantra) instead of giving them the tools to make better decisions right now. And that approach is doomed to fail - thousands of years of evolution and an overpowering biological impulse will see to that, I guarantee it.