Intrauterine RBC Transfusion Dosage

• Cases of severe fetal anemia, i.e., in hemolytic disease of the fetus and newborn (HDFN).
• Hemolytic disease of the fetus and newborn (HDFN) can occur when pregnant females have an RBC alloantibody directed against an antigen expressed on fetal RBCs. When alloimmunization is detected during pregnancy, there is generally regular monitoring of both the antibody titer and the fetal middle cerebral artery ultrasound for signs of anemia. In instances of severe fetal anemia, IUT may be used as a treatment and to suppress fetal erythropoiesis.
• There are other rare indications for IUT that can be determined by specialists in high risk pregnancy.

• Determining fetal weight and fetal hematocrit both involve ultrasound-based estimations.
• A pre-transfusion specimen at the time of umbilical vein access can be used for a direct antiglobulin test (DAT), fetal blood type, RBC antigen typing, bilirubin, hemoglobin/hematocrit, and platelet count.
• Transfused blood for IUT should be group O, negative for antigens against which mother has alloantibodies, crossmatch compatible with mother’s plasma, irradiated, CMV seronegative and/or leukocyte reduced, and hemoglobin S negative.
• Some experts recommend upper transfusion volume limits for IUT in order to avoid complications such as hyperviscosity and increased umbilical venous pressure. 
• Hematocrit of tranfused units varies by the type of storage solution, ranging between 55-85%; for specific information, contact your local blood bank or maternal-fetal medicine expert.

HDFN can have severe consequences, including fetal loss. While IUT can successfully treat HDFN in many instances, it also comes with associated risks. Determining proper volume of RBCs to transfuse to appropriately increase fetal hematocrit is an important step in this process.