BACKGROUND: The aim of this study was to compare the reproducibility, agreement, and sensitivity of pulsed-wave Doppler tissue imaging (DTI) versus spectral Doppler assessment of right ventricular (RV) myocardial performance index (MPI) in midgestation fetuses in both a normal and a disease state. METHODS: RV MPI was calculated using pulsed-wave DTI and spectral Doppler in normal pregnancies (n = 69) and in women with pregestational diabetes (n = 51). Intraobserver and interobserver variability and agreement were evaluated using Bland-Altman analysis. Student's t tests were used for comparisons of differences. RESULTS: In normal fetuses, RV MPI derived by the two methods showed no statistical difference, were interchangeable (DTI, 0.51 ± 0.10; spectral Doppler, 0.50 ± 0.12; P = .686), and were in agreement by Bland-Altman analysis. However, in fetuses of mothers with diabetes, the two methods produced different RV MPI measurements (DTI, 0.56 ± 0.10; spectral Doppler, 0.51 ± 0.12; P < .001). Intraobserver and interobserver bias was lower for DTI. CONCLUSIONS: The DTI method of measuring fetal RV MPI is more sensitive, has less variability and more precision, and is better able to demonstrate subtle abnormalities in cardiac function than the spectral Doppler method in diabetic versus normal pregnancies.