Correlation between middle cerebral artery peak systolic velocity and fetal hemoglobin after 2 previous intrauterine transfusions.

Abstract

The middle cerebral artery peak systolic velocity (MCA-PSV) has been successfully used for timing the first 2 transfusions in fetuses at risk for anemia because of maternal red cell alloimmunization. The objective of this study was to assess whether the correlation between the MCA-PSV and fetal hemoglobin is maintained in fetuses that had undergone 2 previous intrauterine transfusions. Doppler measurement of MCA-PSV was performed before cordocentesis in 39 fetuses. The timing of the third transfusion was based on traditional criteria. The values of MCA-PSV and hemoglobin were expressed as multiples of the median (MoM). Anemia was defined as mild (hemoglobin <0.84 MoM for a given gestational age, moderate (hemoglobin <0.65 MoM), and severe (hemoglobin <0.55 MoM). Regression analysis was used to assess the correlation between the MCA-PSV MoM and fetal hemoglobin MoM. Gestational age at Doppler study ranged from 22 to 35 weeks. Six fetuses (15%) had normal hemoglobin concentration; 21 (53%) had mild anemia; 7 (20%) had moderate anemia; and 5 (12%) had severe anemia. There was a linear correlation between fetal hemoglobin (y) and the MCA-PSV (x): y = 1.185 - 0.341x. Previously, concerns have been expressed about the accuracy of Doppler prediction of anemia after previous transfusions. Our data suggest that there is a good correlation between the MCA-PSV and fetal hemoglobin in fetuses that have undergone 2 previous transfusions. Our findings expand the clinical situation in which Doppler can be used to monitor red cell alloimmunized pregnancies.