The issue is this: does the moral decision result in a victim? Does it have implications for another person?
If so, it is not a personal matter.
Biology science books agree that life begins at conception, so another human being is involved in the abortion, and they are victimized in that their life is ended without their consent.
Contrast this with contraception, which has no victim. Whether or not someone uses a condom is a personal matter...the church can be against it, but government should not be involved because there is no victim.
Abortion has a victim, so it is proper for government to be involved, just like it is with every other type of homicide. We don't say murder is a personal religious choice because it is in the Ten Commandments. It is a personal religious choice, but it is also the proper domain of government because there is a victim.
This is why there is an organization called Atheists for Life. Abortion is not a religious only issue any more than stealing is a religious only issue.