Doppler ultrasound assessment of fetal anaemia in an alloimmunised pregnancy

Introduction While the use of elevated middle cerebral artery peak systolic velocity (MCA PSV) in assessing fetal anaemia is well known, its occurrence is uncommon due to the current practice of giving prophylactic doses of ultrafiltered Rh (D) immunoglobulin (anti-D) in Rh (D) negative women. In mothers who do not receive prophylaxis with Rh immunoglobulin, the overall risk of immunisation for an Rh-positive ABO-compatible infant with an Rh-negative mother is about 16%. With appropriate use of anti-D the incidence of fetal anaemia is approximately 0.1% of pregnancies in Rh (D) negative women. Despite this, maternal Rh alloimmunisation has not been eliminated with subsequent erythroblastosis fetalis and haemolytic disease still occasionally occurring. This article illustrates a case where MCA PSV successfully identified a fetus with anaemia allowing appropriate intervention and a good outcome.