Introduction
Preeclampsia accompanies 2% of pregnancies, and is an important cause of perinatal and maternal morbidity and mortality [1,2] . Preeclampsia is diagnosed when novel onset of hypertension and proteinurea or end-organ damage occurs after 20 weeks of gestation [3] . Eclampsia is diagnosed after seizures without other etiologies are observed in a preeclamptic pregnancy [4] .
In order to prevent seizure, magnesium sulfate prophylaxis is used as a first-choice treatment. It prevents further seizures in eclampsia and any future seizures in preeclampsia [5-7] . When compared with placebo, magnesium sulfate decreases the risk of deterioration from preeclampsia to eclampsia by 60% [8] . Besides prevention of seizures, magnesium sulfate is a systemic vasodilator that elongates sinoatrial impulse production and conduction period [9,10] . Given the cardiovascular effects, magnesium sulfate may affect fetal cardiac function [11] .
The myocardial performance index (MPI) was used by Tei et al in the evaluation of cardiac functions in adult cardiomyopathy. Being a non-invasive method derived from Doppler ultrasound, MPI is useful as a global index of myocardial function. MPI is derived by dividing the sum of the isovolumetric contraction time (ICT) and the isovolumetric relaxation time (IRT) by the ejection time (ET) [12] . Tsutsumi et al. were the first to use MPI to assess fetal cardiac function [13] . Subsequently, Hernandez-Andrade et al. utilized aortic and mitral valve closure and opening clicks on Doppler ultrasound and described the modified MPI (Mod-MPI). This modification increased interobserver and intraobserver reproducibility and reliability [14,15] .
There are studies that have investigated preeclampsia and fetal cardiac function by MPI but they did not find any significant difference [16,17]. However, there is no previous study that aimed to evaluate the effect of magnesium sulfate prophylaxis used for prevention of seizures in preeclamptic/eclamptic pregnant women on fetal cardiac function. Therefore, this study was designed to assess the effect of magnesium sulfate seizure prophylaxis on fetal cardiac function using Mod-MPI.

Methods