Detection of fetal anaemia: comparison of middle cerebral artery peak systolic velocity and liquor OD450

Abstract

Fetal anaemia may arise from haemolysis or failure of production of red blood cells (RBC). Management has included use of previous history, antibody levels (in isoimmunised pregnancies) and amniocentesis for spectrophotometric examination of liquor. This is an invasive procedure with risk of adverse outcome and little efficacy when anaemia is due to decreased RBC production. Recently, Doppler velocimetry as a noninvasive method to detect fetal anaemia has been advocated with increased peak systolic velocity (PSV) in the fetal middle cerebral artery (MCA) allowing detection of anaemia from any cause. This is a preliminary retrospective comparison of MCA PSV with OD450 from amniocentesis. Forty-five cases were identified retrospectively where fetal anaemia was suspected. MCA PSV was performed before amniocentesis in 21 cases. Twenty-four cases where MCA alone was performed are included. Results were compared with fetal or cord blood sampling taken within 7 days of the screening tests. Sensitivity, specificity, positive and negative predictive values were 80%, 60%, 80% and 60%, respectively, for MCA PSV and 50%, 86%, 88% and 46% for OD450. Receiver operator characteristic (ROC) curves were produced. The area under the curves were 0.79 and 0.77, respectively. Both OD450 and MCA PSV perform well as screening tests for fetal anaemia. MCA PSV is non-invasive, thus is the preferred choice in the management of suspected fetal anaemia.