You're making the assumption that the life of an innocent child is more precious to society than the bodily integrity of an innocent woman. I would argue that this is not true, since we don't have a history of forcing even parents of dying children to donate blood or organs to save their lives. You can certainly argue that it should be, but it has not been, traditionally.
“You’re making the assumption that the life of an innocent child is more precious to society than the bodily integrity of an innocent woman.”
No, I am not making that argument or assumption. I make no appeal to the value that society places on someone’s life or bodily integrity. I am making an appeal to the inherent, natural rights that both parties in the dispute have claim to. They don’t derive these from society, so really, society has nothing to say in the matter of any importance. The society could be China, which places less value on the lives of children, or some society that places greater value on them, and the argument would still be exactly the same. Morality and justice don’t change depending on the standards or prevailing attitudes of the populace.