Management of red cell alloimmunisation in pregnancy: the non-invasive monitoring of the disease.

Haemolytic disease of the fetus and newborn (HDFN) due to red cell alloimmunization was a significant cause of fetal and neonatal morbidity and mortality until the introduction of anti-D immunoglobulin, which has dramatically changed the incidence of the disease. However, it is still a major problem in affected pregnancies. The emphasis of current clinical management has shifted from an invasive approach to non-invasive monitoring of the disease. The key elements of the modern management are determining which fetuses are at risk of HDFN with the use of cell-free fetal DNA in maternal plasma (fetal RHD genotype) and the follow-up of antigen positive fetuses by Doppler ultrasonography to detect anaemia severe enough to need treatment. When anaemia is suspected, an invasive approach is still required in a timely manner for confirmation of the degree of anaemia and to administer blood transfusions. This non-invasive approach prevents unnecessary administration of human-derived blood products, with the consequent ethical and cost implications and most importantly avoids iatrogenic conversion of mild to severe disease by avoiding need for techniques such as amniocentesis. The potential problem of the non-invasive approach is the reduction in the total number of invasive procedures, with the subsequent difficulty of maintaining the skills required to perform them.