Invasive versus non-invasive testing in red-cell alloimmunized pregnancies

Amniocentesis for amniotic fluid bilirubin levels is the most widely used t est to predict the severity of fetal disease in red-cell alloimmunization. Many textbooks and guidelines recommend serial amniocentesis to monitor the se pregnancies. However, the reliability of amniotic fluid bilirubin measur ements has been questioned. Two strategies have been proposed by investigat ors. Some advocate liberal or primary use of fetal blood sampling, while ot hers promote the use of non-invasive ultrasonography and Doppler. The purpo se of this literature review is to examine the usefulness of amniocentesis, ultrasonography and Doppler to predict the degree of fetal hemolytic anemi a. The evidence suggests that amniotic fluid bilirubin measurements are of limited value in the second trimester. Furthermore, critical appraisal of t he very few prospective studies is hampered by limitations in design or ins ufficient data given by the authors. Many ultrasound and Doppler parameters have been proposed as useful indicators of fetal anemia. The most promisin g of these methods are Doppler assessment of umbilical venous and middle ce rebral artery flow velocities. We speculate that the accuracy of these non- invasive tests may be good enough to incorporate them in management protoco ls, possibly replacing amniocentesis. Well-designed prospective studies are needed to prove this hypothesis. (C) 2000 Elsevier Science Ireland Ltd. Al l rights reserved.