This technique is now common practice in the treatment of fetal anaemia. Fortunately fetal anaemia has become a rare condition with the widespread use of Anti-D injections in blood group negative pregnant women. Rhesus incompatability is still the most common cause of fetal anaemia. In this condition the mother with blood group negative blood develops antibodies (immune reaction) to fetal red blood cells (blood group positive). 85% of the normal population are blood group positive and 15% are blood group negative. If the mother has a high concentration of these antibodies these can cross the placenta and start destroying the fetal red blood cells and the baby becomes anemic. This is called isoimmunisation.
Most isoimmunisation is related to D antigen. However, a significant proportion arises from exposure to atypical antigens. Other causes of anaemia include fetal infections such as parvovirus or cytomegalovirus (CMV) and genetic blood disorders such as Thalassemia. Severe anemia can cause hydrops (swelling), heart failure, brain damage, intrauterine death or still-birth.
Blood tests: maternal antibody titres can be done monthly to observe levels. Ultrasound is done to monitor fetal well-being and look for signs of heart failure and hydrops. Ultrasound can be used to measure how fast the blood is flowing in the major arteries in the fetal brain and this can provide a fairly accurate assessment on whether or not the fetus requires a blood transfusion.
Prior to transfusing, cordocentesis is performed and blood count level (haemoglobin) is taken, so that we can accurately determine how much blood is needed to transfuse the fetus. Other tests, such as chromosomes, blood group and antibody count can also be done on the cord blood.