Non-invasive tests to predict fetal anemia in Kell-alloimmunized pregnancies.

Objectives To compare test characteristics of ultrasound and Doppler parameters in the prediction of fetal anemia in Kell-alloimmunized pregnancies. Methods In this prospective study, 27 fetuses at risk for anemia due to Kell alloimmunization were evaluated with ultrasound and Doppler imaging. Spleen perimeter, liver length, middle cerebral artery (MCA) peak systolic velocity and intrahepatic umbilical venous (IHUV) maximum velocity were measured. Results were compared with fetal hemoglobin values at first intrauterine blood sampling or delivery. Severe fetal anemia was defined as a hemoglobin deficit of at least 5 SD below the mean for gestational age. Results Eighteen fetuses were anemic and required intrauterine transfusions. In the other nine pregnancies no transfusions were performed; one of these fetuses was severely anemic at birth. MCA and IHUV flow velocities were the best predictors of fetal anemia in Kell alloimmunized fetuses (sensitivity 89% for each test). Sensitivities for spleen perimeter (15%) and liver length (14%) were disappointing. Conclusions Doppler evaluation of MCA peak systolic velocity and IHUV maximum velocity can be used to reliably predict severe fetal anemia in Kell alloimmunization. [ABSTRACT FROM AUTHOR]