What you don't seem to understand or care about is that making abortion illegal will not stop these women from seeking one. It will just force them to go riskier routes to achieve one. Coat hangers, drug overdoses, throwing themselves down staircases, or going to some quack "doctor" who uses unsanitized instruments. Not only with the fetus probably not survive, but the mother is at great risk herself.
And who are you to tell these women not to have sex? Do you know their situation? Maybe they were raped and are too embarrassed or scared to tell someone, or maybe they're in an abusive relationship. Maybe they're happily married and their birth control failed. Maybe birth control simply does not work for them. One of our users, CaryFairy, can't use hormonal birth control and has gotten pregnant multiple times on other forms.
Abortion is legal because these women deserve proper medical treatment. If they've made their mind up to have an abortion, they deserve to have one that is quick, sanitary and safe. If you want to stop abortion, you need to try another route. You need to research ways of making birth control more widely available for teenagers and women. You need to volunteer in women's shelters and support groups for rape and abuse. You might want to volunteer at a crisis pregnancy center that offers alternatives to abortion, or volunteer at an adoption agency.
Trying to make abortion illegal is tackling the symptom, not the cause. If you really want to do something about it, you need to get to these women before they've had to make the decision to do this. And that includes NOT making them feel guilty for being a human being and having sex. If you're really going to preach abstinence, you won't get far at all. Try to understand these women, their needs and desires, and their motives, and you might actually make some progress.