Middle cerebral artery Doppler velocimetric deceleration angle as a predictor of fetal anemia in Rh-alloimmunized fetuses without hydrops

OBJECTIVE: The purpose of this study was to evaluate the screening performa nce of a new middle cerebral artery Doppler velocimetric index for the pred iction of fetal anemia. STUDY DESIGN: Doppler velocimetry of the middle cerebral artery was perform ed before cordocentesis in 24 Rh-alloimmunized fetuses without hydrops on 5 2 occasions. The angle between the line describing the average slope during the diastolic phase of the cardiac cycle and the vertical, the middle cere bral artery standardized deceleration angle, was measured. The deceleration angle values were expressed in multiples of the median for gestational age . The screening performances of deceleration angle for the prediction of an emia (difference between expected mean hemoglobin level and measured value greater than or equal to 2 g/dL) and severe anemia (hemoglobin deficit grea ter than or equal to 5 g/dL) were determined. RESULTS: The mean (+/-SD) gestational age at cordocentesis was 28.6 +/- 5.7 weeks' gestation. The risk of fetal anemia increased with decreasing decel eration angle values. The sensitivity and false-positive rate for the detec tion of anemia in cases with no previous transfusions tone measurement per patient) were 72.0% and 13.3%, respectively; among those with one previous transfusion the values were 90.0% and 0.0%, respectively. For severe anemia the corresponding values were 100% and 0%, respectively, among those with no previous transfusions and 100.0% and 16.7%, respectively, among those wi th one previous transfusion. There was no risk of severe anemia when the an gle was >0.9 multiples of the median. The risk of anemia was significantly reduced with an angle greater than the median for gestational age (decelera tion angle >1.0 multiples of the median; relative risk, 0.09; 95% confidenc e interval, 0.02-0.37). The risk was significantly increased with an angle less than the median for gestational age (deceleration angle <1.0 multiples of the median; relative risk, 30.0; 95% confidence interval, 5.9-158.4). CONCLUSION: The risk of fetal hydrops is remote in the absence of severe an emia. With a new Doppler velocimetric index in the middle cerebral artery t he risk of severe anemia was found to be low when the deceleration angle wa s >0.9 multiples of the median. Anemia can also be predicted with this inde x. The high sensitivities and acceptable false-positive rates support the p otential clinical applicability of the method to reduce the reliance on cor docentesis in Rh alloimmunization. Our findings appear to validate the util ity of the deceleration angle for the prediction of fetal anemia.