An intrauterine transfusion provides blood to an Rh-positive fetus when fetal red blood cells are being destroyed by Rh antibodies. A blood transfusion is given to replace fetal red blood cells that are being destroyed by the Rh-sensitized mother's immune system. Fetal anemia occurs when the baby's blood count is too low. The condition can be life-threatening, which is why fetal blood transfusions need to be conducted shortly after discovering fetal anemia. A fetal blood transfusion replaces the red blood cells that may have been destroyed by an infection or Rh incompatibility.