Noninvasive diagnosis of anemia in hydrops fetalis with the use of middle cerebral artery Doppler velocity

Objective: The purpose of this study was to assess the value of the middle cerebral artery time-averaged mean velocity for the detection of anemia as the cause of fetal hydrops. Study design: We examined 17 pregnant women with fetuses with hydrops (with ascites as the main component of hydrops) and who were considered at risk for anemia because there was no obvious explanation for the hydrops on the initial scan. Assessment included the measurement of the middle cerebral artery time-averaged mean velocity by color flow Doppler scan, followed by fetal blood sampling for investigations that included fetal hemoglobin. We investigated the correlation between increased middle cerebral artery time-averaged mean velocity (>2 SDs for gestational age) and fetal anemia (<2 SDs for gestational age). Results: Eleven fetuses had anemia; 3 of the fetuses had red cell antibodies, and 6 of the fetuses had normal hemoglobin. There was a strong negative correlation between the middle cerebral artery time-averaged mean velocity and the hemoglobin values (r=-.9; P<.0001). The mean (z score) of middle cerebral artery time-averaged mean velocity for fetuses with normal hemoglobin was 1.1 +/-0.81 and for the fetuses with anemia was 4.71 +/-2.16 (P<.001). The sensitivity for the increased middle cerebral artery time-averaged mean velocity to predict fetal anemia was 91%, and the specificity was 100%. Conclusion: The middle cerebral artery time-averaged mean velocity is significantly increased in cases of hydrops caused by anemia, including cases other than red-cell alloimmunization. These findings can be useful for counseling and treatment and allow the investigation of the cause of hydrops without awaiting blood for intrauterine transfusion in patients who are very unlikely to be anemic and often avoids 2 procedures in those patients who require transfusion. Larger studies are required to further confirm these findings.