I definitely get what y'all are saying, but here's the thing:
You can't prevent other people from having sexual relationships, whether by law or by just advising someone. If you could, there would be almost no need for abortion. (It would be very nice if it could be so, but unfortunately that's not how the world works.)
Often people can't prevent themselves from engaging in sexual relationships. There is just too much pressure, and people who aim at abstinence often do not reach it. Unfortunately, people are made with a drive to engage in sexual relationships. It just happens.
I don't think abortion is right, but it should stay legal in all cases. This is because if there are only certain criteria allowed for having abortions, an abortion will be refused if the criteria can't be proven to be true. Proven, in court.
Think about it. Rape is less uncommon than is usually believed, or than the statistics suggest. The reason: it's hard to admit you've been raped. People have feelings of disbelief, embarrassment, and panic after such a traumatic event. And if you force yourself to admit it, you'll end up on trial, against the man who offended you. In court, it's hard to prove whether or not you've been raped, because no one else was there when it happened. (therefore more pregnancies occur through rape than you are aware of)
So if you can only have an abortion in the case of, say, rape, then it's likely that the abortion won't be allowed unless you can prove IN COURT that you were raped.
Although I don't think it's good to get an abortion just because you're pregnant and not totally sure what to do with the child, it should still be permitted, since there are situations like the one stated above. Count on the mother to make that choice, since she's the one responsible for whatever happens. She will undergo whatever repercussions come from the choice she makes.
The solutions to dramatically reduce the necessity of abortion:
make birth control more readily available (and free/low-cost, with education on why and how to use it)
encourage abstinence
improve the adoption system (it's very hard to put up a child for adoption, or to adopt a child, currently)
more police force (to prevent rape, which can cause pregnancy often leading to abortion)
I had a friend, and her mother was 13 when she gave birth to her. They were nice enough, but they had very little money, and lived in a dilapidated apartment on the poor side of town. I felt very bad for this friend, since she had old, torn clothes, and was not treated kindly by other kids at school, mainly because they thought she was "dirty" for the fact that her mother had her out of wedlock. This friend moved away a short time later, but I hear that when she got just a little older, she too became pregnant and involved in the same troubles her mother had. The problem in her family has become a vicious cycle, as it likely has with some others. It probably could have been prevented if they'd known more about birth control. I wish the best for this friend, though I haven't seen her for many years now.
Verdict: keep all choices legal, and let the pregnant woman make that choice.
Edit: refined grammar!