If you want to talk science, then the first thing that must be observed is that the baby is not part of the mother's body. He is *in* the mother's body, but he is not a part of her body. The baby is a separate living being with a unique DNA set, his own blood supply (often with a different blood type than the mother's), his own brain, his own heart, his own eyes, his own limbs, etc., etc.
So the argument "my body, my choice" is scientifically baseless. A more accurate slogan would be "my baby, my choice," but that would be problematic because it would highlight that the "choice" is whether or not to allow the baby to live. It would be a much more honest argument, but it would be tantamount to saying, "I should be allowed to kill my baby if I decide I don't want the baby."
As I often say, "My body, my choice" is fine...the problem is, there is a second body involved. If it wasn't so, there would be no reason for all of this debate.
This is absolutely not true. If the fetus was truly a separate body it could not survive.