If a woman has Rh negative blood and becomes pregnant with an Rh positive child (because the father is Rh positive), the child may be born with a disease known as erythroblastosis fetalis. However, this does not always occur. The first child is usually healthy (and often later ones) unless the mother has previously received blood transfusions with Rh positive blood, and this is becoming rare due to greater care in giving transfusion. ONLY ONE IN 25 OR 50 Furthermore, only about one woman in 25 or 50 with Rh negative blood and an Rh positive husband becomes sensitive and gives birth to a baby with erythroblastosis. It should be pointed out also that, even if a child does have erythroblastosis, much can often be done by giving blood transfusions after birth. Whereas three quarters of the infants with erythroblastosis formerly died, now nine out of ten can be saved with the right kind of transfusion. To summarize the situation: If both parents are Rh positive there is little to worry about. If the mother is Rh positive and the father Rh negative, there is nothing to worry about. If the mother is Rh negative and the father Rh positive occasional trouble can be anticipated, but this is by no means inevitable.