Monochorionic twin pregnancies, characterized by a single shared placenta with vascular anastomoses, create unique hemodynamic conditions that affect fetal cardiac development. The continuous exchange of blood between fetuses exposes the myocardium to variable preload and afterload, leading to adaptive structural and functional remodeling. This review summarizes current evidence on myocardial changes in monochorionic twin fetuses, focusing on hemodynamic, morphologic, and biochemical aspects. Data from echocardiographic and molecular studies indicate that even in uncomplicated cases, the fetal heart exhibits concentric hypertrophy, increased wall thickness, enhanced longitudinal systolic function, and early signs of diastolic stiffness. Elevated concentrations of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) reflect myocardial stretch, while activation of hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) pathways suggests metabolic and angiogenic adaptation. These findings demonstrate that the myocardium in monochorionic twin fetuses undergoes continuous physiological remodeling to maintain cardiac output under shared circulatory load. Although primarily compensatory, these changes may predispose to later cardiovascular vulnerability, emphasizing the need for careful prenatal and postnatal cardiac surveillance in monochorionic twin gestations.

Monochorionic twins, fetal heart, myocardial remodeling

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