Well, FLMC might have an interesting point. Terminating the life of an unborn human should have the same moral weight (good or bad depending on your view) no matter the circumstance of the mom - married or unwed. For the sake of this discussion, such a piece of information may inform the discussion though.
According to the Alan Guttmacher Institute (Research buddies of Planned Parenthood) "All in all, 17% of abortions in the United States occur to married women." (http://www.guttmacher.org/pubs/tgr/06/2/gr060210.html)
Now my question to FLMC would be an echo of Basset's. Why does that matter?