Mainstay therapy for fetuses affected by maternal red cell alloimmunization is serial IUT (intrauterine transfusion). Testing to determine when fetal red cells have been replaced with donor cells historically involves the use of the KB (Kleihauer-Betke) test. Hgb (Hemoglobin) electrophoresis testing may be more rapid with a reduced cost of analysis. We aimed to determine the correlation between fetal Hgb electrophoresis versus the traditional KB test. This is a retrospective analysis on all alloimmunized singleton pregnancies undergoing IUT between 1/1/2021 and 7/1/2023. Maternal and fetal characteristics were collected along with indication for IUT. A final fetal blood sample was obtained at the conclusion of each transfusion and sent for KB testing and Hgb electrophoresis. The primary outcome was the assessment of these parameters in their ability to predict replacement of the fetal circulating red cell population with donor cells. Linear regression analysis and repeated measures analysis of variance were performed, P values less than 0.05 were considered significant. A total of 56 IUTs were performed in 16 patients. There were 39 (69.6%) final KB test values collected and compared to 30 (53.6%) final Hgb electrophoresis values. Hgb electrophoresis when compared to the KB test demonstrated a significant correlation (R2 = 0.93; 95% confidence interval, 0.61-0.76; P <0.001). This same finding held true when examining correlation at each individual IUT as well. The final KB test and Hgb electrophoresis value significantly decreased with each transfusion (P=0.003). A predominance of adult donor blood was noted by the third transfusion for both laboratory indices. Fetal Hgb electrophoresis obtained at the time of IUT demonstrates a significant correlation with the traditional KB test.