OK, I'll try once more. An appendage is attached to the trunk of something. The blood flowing through it and its genetic code are identical to the person or thing it is attached to and absent disease it poses no danger to that person unless it gets caught in the zipper.
A baby on the other hand has its own unique genetic code, its own blood supply and a placental barrier that seperates Mom and Baby? Would you care to know why that placental barrier exists?
appendage:
1 : an adjunct to something larger or more important
2 : a subordinate or derivative body part; especially : a limb or analogous part (as a seta)
A woman's fetus is an appendage of the woman and is the woman's property.