ACP Broadsheet No 150. March 1997. Antenatal serological testing and prevention of haemolytic disease of the newborn.

Introduction Routine antenatal serological screening has been practised throughout the United Kingdom and worldwide for about 30 years.' Originally introduced to detect pregnancies at risk of haemolytic disease of the newborn (HDN) due to Rh anti-D antibodies, its continued use has led to an increasing realisation of the clinical importance of other red cell antibodies in the pathogenesis of HDN. Three factors are essential in the pathogenesis ofHDN: maternal red cell antibodies must cross the placenta, the fetal red cells must possess the appropriate red cell antigen against which the antibodies are directed, and the antibodies must be capable of causing immune destruction. The clinically relevant antibodies are, therefore, virtually always IgG and reactive at 37°C. About 2-5% ofwomen will have such antibodies as a result of transfusion, pregnancy, or both; it is, therefore, important for the pregnant patient, the fetus, and their clinical advisors that appropriate antenatal screening tests are performed.