**1. Introduction**

During pregnancy, the maternal body undergoes significant hemodynamic changes to ensure normal fetal growth. On average, maternal cardiac output can increase up to 30%–45%, resulting mostly from the intensified metabolism, increased circulating blood mass, the appearance of an accessory placental circulatory system, and finally, a gradual increase in body weight during pregnancy. Although blood volume increases, the systemic blood pressure in a healthy mother undergoes no significant changes. This is mainly due to a decrease in total peripheral vascular resistance, primarily at the arteriolar level. The mammalian placenta is also important for the regulation of both the maternal and fetal circulations. Adequate uterine blood flow is critical to fetal growth and development [1]. Fetal heart undergoes functional changes: throughout gestation, the fetal myocardium becomes more compliant and making ventricular filling less dependent on atrial contraction. Both the increase in size and the maturational changes lead to a tremendous increase in cardiac output [2].
