<p>Background: Echocardiographic indicators may be useful as an alternative method to determine the appropriate time for intervention, especially when Doppler assessment of the middle cerebral artery peak systolic velocity (MCA-PSV) is inconclusive. In this study, arterial duct blood flow and cardiac output of fetuses with Rh alloimmunization-related anemia were compared before and after intrauterine transfusion (IUT).<br /> Methods: Fifty intrauterine blood transfusions were performed on anemic fetuses in this study. All cases were attributed to Rh alloimmunization, detected with MCA-PSV Doppler ultrasound imaging assessments. They all underwent intrauterine blood transfusion and echocardiographic assessments a day before and 24 <em>hr</em> after the procedure. The measured cardiac indices included the velocity time integral (VTI) of the aortic and pulmonary valves, the ductus arteriosus acceleration-to-ejection time (AT/ET) ratio, and the MCA-PSV. Analyses were performed in SPSS v24 (p&lt;0.05) using paired t-tests for mean differences and Pearson&rsquo;s correlation for associations between continuous variables.<br /> Results: Aortic and pulmonary valve VTI, MCA-PSV, and ductus arteriosus AT/ET ratio significantly decreased after intrauterine blood transfusion (p&lt;0.001). The aortic valve VTI and ductus arteriosus accurately detected anemia, with areas under the receiver operating characteristic (ROC) curve of 99.9% and 98.9%, respectively.&nbsp;<br /> Conclusion: All the measured parameters showed significant changes after intrauterine blood transfusion. Aortic valve VTI and ductus arteriosus AT/ET ratio seem to have the highest accuracy in detecting anemia. Echocardiographic assessment can be beneficial in defining the appropriate time for intrauterine blood transfusion in cases where MCA-PSV is inefficient.</p>