Abortion in Cases of Rape, Incest, Disability?

There are those who think your position on abortion is extreme because you wouldn't even permit it in cases of incest, rape, or when the child is defective. How do you justify such a position?
Only in rare instances when the life of the mother is literally at stake do I feel we have the moral authority to destroy a developing fetus. My reasoning is based on this simple question: Is there any fundamental difference between a baby who resides in his mother's uterus and one who has made an eight-inch journey down the birth canal? If so, what is that difference? At what point in the birth process does God's mantle of humanness fall upon an individual? Is there anything particularly mystical about the expulsion from the mother's body that could account for a transformation from mere protoplasm to a human being with an eternal soul? I think not. Surely the Lord does not look upon the baby inside the uterus with any less love and concern than one who enters the world a few minutes later. The only difference between them is that one can be seen and the other cannot.
If that premise can be accepted, then it is equally immoral to kill either those born or those yet to be born. Physical and intellectual health and the nature of conception are irrelevant to the issue. Even most pro-abortionists would not propose that we destroy children arriving in the delivery room with unexpected deficiencies. Indeed, the authorities would charge them with murder for killing a neonate who lacked adequate cognitive function or who had only a few weeks to live. We would be obligated morally and legally to let nature take its course, regardless of the severity of the baby's condition. Likewise, we would not kill a one-day-old infant who was conceived in a rape or an incident of incest.
Once born, the deliberate destruction of life is unthinkable. Why, then, is such a baby considered "fair game" when he resides within his mother's uterus? It is true that the law sometimes recognizes a different status for those born versus those unborn, but the law in those instances is wrong. There is no biological or moral basis for this distinction. Infanticide merely seems acceptable when we don't have to witness the death process of a tiny victim we have not yet met.
Therefore all the arguments in favor of terminating the defective or handicapped unborn child must be weighed against this understanding, including, "he's going to die anyway," "he'll only suffer if we let him live," "his life will only bring pain to his parents," "he has no chance of living a normal life," and "this is really the best way out for everyone concerned." When applied to the baby who has managed to limp into this world, the evil of these rationalizations becomes apparent. No justification will permit us to give a newborn a lethal injection of cyanide. But hours earlier, when the mother's contractions have not yet begun, some would feel righteously justified in tearing the same defective or ill-conceived infant to pieces. The proposition is categorically immoral in my view.
I am aware that these views are infinitely easier to articulate from a philosophical or theological perspective than they are for the mother or father who must face them personally. Of special concern is the woman who is carrying a baby conceived during a rape. Her pain and agony are beyond expression. I am convinced, however, that such a mother, if she carries the baby to term and either keeps her baby or places it up for adoption, will never regret her decision. What is right and moral for the unborn child is ultimately best for the mother and father, too. I know this statement will be inflammatory to some, but it is what I sincerely believe.