Some years ago a biology professor told me that about four out of five pregnancies result in miscarriage, usually before the woman even knows she's pregnant. He said this fact was discovered when they first started in vitro fertilization. It had a huge failure rate. On further investigation they found that was the norm in nature as while.
I had not heard of this before or since. A little research seems to back my professor.
So my question is: Why doesn't this come up in abortion debates?
It would seem to turn the anti-abortion crowds' argument on it's head, at least for the sort who believe legal status should be confered on a fertilized egg.