The myocardial performance index (MPI) was first proposed by Tei et al. as a means of assessing heart function in patients suffering from dilated cardiomyopathy. The MPI derived from Doppler has shown potential as a non-invasive measure of global myocardial function. The maximum pressure index (MPI) is obtained by subtracting the ejection time (ET) from the total isovolumetric contraction and relaxation times (ICT and IRT, respectively). Tsutsumi et al. were the first to note that the MPI might be used to assess the fetal heart's overall function. The MPI has been proposed by other researchers as a potential useful tool for predicting fetal cardiac adaptation alterations in complicated pregnancies involving growth-restricted fetuses, fetuses of diabetic mothers, fetuses (including hydropic fetuses), and fetuses with Rh sensitization. Conversely, reference MPI values for left fetus cardiac assessment span a wide range in published literature. The big difference between the usual reference values is believed to be caused by the lack of distinguishing characteristics in the Doppler waveforms that were used to calculate the time-periods. In an attempt to circumvent this problem, other authors have proposed different alternatives. The Mod-MPI, developed by Hernandez-Andrade et al., is an adaptation of the myocardial performance index. Improved agreement and lower variation compared to the original MPI were seen with this adjustment, which is based on Doppler echoes of the aortic and mitral valves. Due to its new addition to the literature, Mod-MPI has not been used to evaluate fetal cardiac function in relation to pregnancy-related complications.