A fetal transplant? You're kidding right? For one thing it's never been done. A woman's body grows a placenta alongside the fetus, so there wouldn't be anywhere on a regular body to put a fetus. You'd have to transplant the entire setup - placenta, fetus, and probably parts of the uterus. Also, a pregnant woman's body is a cocktail of hormones. Without those hormones, the baby dies. Even if you got the host on the exact right hormones, it would still attack the new placenta fetus because the DNA wouldn't match. Immunosuppresents would probably kill the baby.
I am alive today because some one developed a procedure that had never been done.
They are today developing an artificial womb so pervert homos can pretend to have a child.