For Christmas and thinking about the Baby Jesus, Bob Enyart asks Joseph Kezele, M.D., three questions. As a rule, the blood of the child in the womb and of his mother don't mix. So how can it be that the baby's blood gets its oxygen and nutrients from the mother's blood? And if we adults make our blood cells in our bone marrow, where does the unborn child makes his? Then finally, because the baby gets his oxygen from mom and not from his own lungs, there must be significant changes at birth in the child's circulatory system. So what changes in the circulatory system architecture happen at birth? Dr. Kezele received his M.D. from the University of Arizona.