If your red blood cells contain a substance known as rhesus factor, you are rhesus, or Rh, positive.  If a woman who is Rh negative conceives a baby by a man who is Rh positive and the baby, in turn, is Rh positive, the woman may become sensitized to the Rh positive blood at the time of delivery.  If a subsequent baby is also Rh positive, the mother's body recognizes the baby's … [Read more...]