One of the government's role (at least in the US) is to protect the individual from others. That's why we have laws ...
Murder harms another, so there's a law.
Rape harms another, so there's a law.
Theft harms another, so there's a law.
If life begins before birth, shouldn't that citizen be protected from harm by others? If it doesn't, shouldn't abortion on-demand in the ninth month be perfectly okay?