Subclinical Cardiovascular Adaptation in Uncomplicated Monochorionic Twin Pregnancies: Echocardiographic and Cardiac Biomarker Findings

Background: Although cardiac involvement is well characterized in complicated monochorionic (MC) pregnancies, whether subtle cardiovascular changes occur in uncomplicated pregnancies remains unclear. We characterized fetal and neonatal cardiovascular adaptation using echocardiography and cardiac biomarkers. Methods: In this prospective longitudinal cohort, 76 dichorionic (DC) and 68 uncomplicated monochorionic diamniotic (MCDA) twins underwent fetal echocardiography at 28 weeks and neonatal echocardiography within 72 h after birth. Cord blood N-terminal pro-B-type natriuretic peptide (NT-proBNP), high-sensitivity cardiac troponin I (hs-cTnI) and heart-type fatty acid-binding protein (H-FABP) were assessed at delivery. Analyses used generalized estimating equations to account for within-pregnancy clustering and Benjamini–Hochberg correction for multiple comparisons. Associations between cardiac biomarkers and fetal echocardiographic parameters and interactions with chorionicity and gestational age at birth were also evaluated. Results: MCDA fetuses showed trends toward a higher cardiothoracic ratio, lower right ventricular fractional shortening and tricuspid annular plane systolic excursion, and a higher prevalence of tricuspid regurgitation (TR) compared with DC fetuses. In the early neonatal period, nominal differences in interventricular septal thickness and tissue Doppler indices did not persist after FDR correction. Cord-blood hs-cTnI (21.83 vs. 12.29 pg/mL; p = 0.015, FDR-adjusted p = 0.027) and NT-proBNP (1327.6 vs. 887.6 pg/mL; p = 0.018, FDR-adjusted p = 0.027) concentrations were higher in MCDA twins. After gestational age adjustment, the association with hs-cTnI remained relatively stable, whereas that with NT-proBNP was attenuated; neither remained significant after FDR correction (p = 0.116 for both). The TR-hs-cTnI association differed by chorionicity (p for interaction < 0.001, FDR-adjusted p < 0.004) and persisted after adjustment for gestational age at birth. Conclusions: Conventional echocardiographic measures of cardiac structure and function appear to be largely preserved in uncomplicated MCDA twins during fetal life and the early neonatal period. Higher cord-blood hs-cTnI and NT-proBNP may suggest subclinical myocardial stress associated with monochorionicity, although gestational age-adjusted findings warrant caution.