Longitudinal reference ranges for serial measurements of myocardial performance index (MPI) by conventional and pulsed-wave tissue Doppler in monochorionic diamniotic twins at 17 to 26 weeks of gestation

Objective: To describe the longitudinal changes of fetal myocardial performance index (MPI) measured by conventional Doppler (MPI) and by pulsed-wave tissue Doppler (MPI′) based on a prospective cohort of uncomplicated monochorionic diamniotic twin. Method: Single-center observational study. We measured MPI and MPI′ in the right and left ventricles 3 times between 17 and 26 weeks of gestation. Second-degree fractional polynomials were built to obtain the best fitting curves in relation to gestational age (weeks) for each parameter. Gestational age-specific reference values were estimated by using two-level hierarchical models. Results: Eighty-three uncomplicated monochorionic pregnancies were included in our study with a total of 249 observations. Fetal cardiac function was measured as MPI RV and LV, MPI′ RV and LV at a mean gestational age of 18+3(range 17+1to 19+2), 22+3(21+1to 23+5), and 24+3(22+6to 26+2) weeks. The reference ranges for MPI LV, MPI RV, MPI′ LV, and MPI′ RV at 17 to 26 weeks were constructed and conditional percentiles calculated. Conclusion: The present study provides additional data on fetal cardiac function in uncomplicated monochorionic diamniotic twin gestations, describing the evolution of MPI and MPI′ in both ventricles in uncomplicated monochorionic diamniotic pregnancies.