It's not highly unlikely, anyone who is able to ovulate has the chance of pregnancy, during or not during their period. And that's not the issue, the issue is no one is teaching safe sex, birth control, and the effects of unsafe sex. Abortion is not wanting to birth a child who is unwanted to put either in a unwanted household, with a teenage parent, mostly without a partner to care for them. Their parents not caring for the parent of the child, resulting is major effects to both the parent and child. Not wanting to add a child to the world who will be sent to foster care, abusive households, and orphanages. Or the fact they just did not want them. Less abortions would tend to happen if safe sex (not correlated with any form of religion, or abstinence program) was taught in schools.
But let just say, Abortion is not used as birth control. No one just goes WELL TIME FOR 25TH ABORTION THIS MONTH!! No, the person who is planning the abortion goes through a lot of emotional issues and a lot of thinking goes into this. Some people who thought about abortion, decides not to do it. And that's fine, it's the person's choice to have it.