Sally is 15. She does okay in school, babysits her little sister, and earns some money doing chores around her house and for neighbors. She sometimes smokes cigarettes, but says no to drugs. She has had one boyfriend, but they broke up. Now she's dating a 16-year-old guy from her school, Jimmy, and they are talking about having sex. Sally hasn't learned about preventing teenage pregnancy.

Sally daydreams about being married to Jimmy. In these dreams, she imagines Jimmy coming home to her, and they make love on the floor of their really cool apartment. Sometimes she even imagines they have a baby, and she greets Jimmy at the door holding the baby. Since Sally doesn't want to go to college and doesn't have a job, she really wants to do this. This is a happy picture for her, and she doesn't think twice about preventing teenage pregnancy.

Sally is at risk of getting pregnant soon.

She's at risk of DECIDING to get pregnant and not preventing teenage pregnancy. Maybe she'll tell Jimmy about her wish and he'll go along or maybe she won't tell him; she'll just hint that she's protected and not worry about preventing teenage pregnancy. Why would Sally WANT to get pregnant now? One reason is that she can escape some tough decisions about finishing school, deciding what kind or work to do, even escape deciding whether or not to marry Jimmy. If he's the father of her child, that decision is almost made for her.

If you are reading this and thinking Sally would be very stupid and wrong to not think about preventing teenage pregnancy, you are probably an older teen or in your early 20s. If you are a young girl, you are much more likely to get caught up in the whole romantic picture of husband, apartment, and baby.

I know you don't want to hear this, but teens and adults do not have the same brains. They think and reason in different ways. Until you get past your early 20s, part of your brain (the prefrontal cortex) is NOT FULLY DEVELOPED! That is the part of your brain that controls judgment, planning for the future, and understanding the consequences of your actions (like preventing teenage pregnancy). Your whole life may hang in the balance, but you do not have the brain you need (yet) to think through your choices and make a good decision about preventing teenage pregnancy.

Now let's change the story a little. Let's have Sally meet Jimmy at a party and end up in a car with him. He's a hot, popular guy. He's hot for Sally! She's feeling waves of desire and something she labels as love! They have no condoms, no birth control (not to mention STD protection), and no way of preventing teenage pregnancy. Does she go all the way?

There's a good chance that she will; her underdeveloped prefrontal cortex should be screaming about disease, preventing teenage pregnancy, possible cruel rejection by Jimmy, and gossip all over the school but, instead, her feelings are likely to take over completely. Many girls love intensity, romance, risk, living for the moment, even self-destructive behavior. The voice of reason is so easily overwhelmed by impulses. It's an old, old story. The only new part is our understanding of how the immature teenage brain contributes to the story.

What should a girl do to help prevent teenage pregnancy? It's very hard to accept that YOU are not capable of making wise decisions for yourself, that your brain is not yet up to the careful calculations needed to act on your own best long-term interests. But you aren't. In the meantime, all you can do is try to remember that even your most cherished longings and emotions could be your worst enemy. Just think of Romeo and Juliet! Find someone over twenty-five you trust and can talk to about teenage pregnancy, and try to postpone ALL important decisions until you've had time to talk things over with her or him. Reverse the Nike tag line and DON'T just do it! Wait, talk, and think about preventing teenage pregnancy.

An important afterword: We've been taking a scientific view of the teen sex and teen pregnancy issues, but there are many other perspectives on these issues, one of which is the religious or spiritual perspective. Almost all religious leaders favor preventing teenage pregnancy through sexual abstinence until marriage. This message is simple, deeply-ingrained, and reinforced by families and even by many schools. So the next time you feel like groaning about the "Just say no," message, remember that in a pinch some night, it may help to compensate for the brain cells you don't yet have and save your future by preventing teenage pregnancy.