ALSO KEEP IN MIND: Correctly identifying the persistent vegetative state is much more difficult than identifying either a coma or actual brain death, and less-informed folks might think the PVS is equivalent to BD. I could easily imagine someone thinking that a doctor was talking about brain death, and a patient recovering from that state, upon learning that the patient was persistently vegetative instead of actually brain dead.
PERHAPS YOU SHOULD STUDY HOW MAMMALIAN EVOLUTION HAPPENED. We are descended from actual egg-layers, remember? And in Nature biological systems don't always work "ideally", which therefore allows oddball things to happen, which might or might not be incorporated into a future different species than before. So, for mammalian reproduction to have BEGUN to happen, we need to first keep in mind that a number of egg-laying species have leathery-shelled eggs, and some "potential shelled egg" must have failed to form correctly, and implanted into its mothers oviduct. DO NOTE the similarity between an amniotic sac and a leathery-eggshell! If it wasn't implanted for very long (something common in marsupials), it could do some growing and detach when developed enough to minimally survive, and the attachment site could have been small enough to not be fatal when ripped out. With something like that as a starting point for surviving genes to pass down the generations, evolution modified part of the oviduct to provide a less-dangerous place for attachment and ripping --less dangerous to the mother. It had nothing to do with providing anything for the unborn mammal, despite the ignorant blatherings of abortion opponents. Keep in mind that even today, if an unborn mammal implants into a not-less-dangerous place, the "ectopic pregnancy" still suffices for the mammal to grow and develop (at least up to the point where it kills its mother). **IT** does not actually need the womb!
THE FUNCTION OF THE UTERUS IS TO SAVE THE MOTHER'S LIFE, from having her guts ripped out when the unborn mammal is finally expelled. That's all. And sometimes it still doesn't work out (fatal hemorrhaging). Pregnancy is a medical condition in which a mammalian female is trying to survive the worse-than-parasitic assaults of the unborn. PERIOD.
