What does that have to do with causing someone else to miscarry?
A) op didnt clarify who was doing the initiation of a miscarriage. There's unclarified ambiguity.
B) charging manslaughter for one person, and providing medical support for another for the same action of facilitating a miscarriage enters a very real legal discourse know as the entire debate around women's rights. If you would like to know more you can review the legal precedents associated therein.