An Intrauterine transfusion (IUT) is a procedure in which blood is transfused into a fetus, most commonly through the umbilical cord. It is used in cases of severe fetal anaemia.
For HDFN to occur, the fetus must have a positive blood group (paternally inherited) and the mother must have negative blood group. Fetal red cells has the Rh factor which is the antigen which the mother does not have. When mother is exposed to the Rh factor during a previous pregnancy or transfusion, mother develops antibodies to the Rh factor.
In the next pregnancy, maternal antibodies cross the placenta during pregnancy and destroy fetal red blood cells (RBCs). This process can lead to fetal anaemia, and in severe cases can progress to hydrops (edema), ascites, heart failure, and death.
However, the rates of these cases have significantly reduced by Anti-D immunoglobulin administration.
Fetal anaemia is monitored throughout pregnancy using Doppler measurement of the middle cerebral artery (MCA) peak systolic velocity (PSV). Once MCA-PSV value exceeds 1.5 MoM, it indicates development of fetal anaemia. At this point, invasive testing via percutaneous umbilical cord blood sampling (PUBS, also called cordocentesis) is done followed by fetal transfusion
Prior to the procedure, the compatible blood is obtained. O, RhD-negative, and antigen-negative for maternal RBC antibodies is selected. The selected blood then undergoes irradiation and leukocyte reduction. Antenatal corticosteroids are typically given to mothers before IUT to anticipate the need for an emergency caesarean section.
The procedure is usually performed in a hospital under sterile conditions. The mother's abdomen is cleaned with an antiseptic solution. She is given a local anaesthetic injection to numb the abdominal area from where the transfusion needle will be inserted. During the procedure, medicine is given to the fetus in its thigh to temporarily stop the fetal movements.
An ultrasound is performed to view the position of the fetus and to help guide the needle. The first step is to locate a relatively stable segment of the umbilical cord. Once a suitable location is established, the needle is inserted through the mother’s abdomen into an umbilical vessel using ultrasound guidance. If insertion into an umbilical vessel is not possible, blood may be transfused into the portion of the umbilical vein in the fetal abdomen].
Prior to the transfusion, percutaneous umbilical cord blood sampling (PUBS) is conducted. The fetal blood sample is drawn and immediately analysed for haematocrit in the hospital haematology laboratory. The result confirms the level of fetal anaemia and indicates the correct amount of blood to be transfused. With the needle still in place, the blood is delivered into the fetus's umbilical cord blood vessel. Following the transfusion, an additional blood sample is drawn and analysed to determine the ending hematocrit level. %.
Fetal survival rates after intrauterine transfusion through the umbilical cord are more than 90% for fetuses that do not have hydrops and about 75% for fetuses that have hydrops
Risks of intrauterine transfusions may include uterine infection, fetal infection, preterm labour, excessive bleeding and mixing of fetal and maternal blood, amniotic fluid leakage from the uterus, slowing of fetal hearty rate, bleeding from the umbilical cord puncture site or (rarely) fetal death. There is only 1-2% risk of such complications.