Cardiac Structural and Functional Assessment of Monochorionic Twin Pregnancies Complicated by Type II and Type III Selective Fetal Growth Restriction.

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Selective fetal growth restriction (sFGR) complicates 10-15% of monochorionic twin gestations. Prior studies reported neonatal cardiac hypertrophy present in 25% of twins impacted by sFGR, most commonly the larger twin (80%). Our primary objective was to characterize fetal cardiac structural and functional echocardiogram findings in sFGR twins. A retrospective cohort analysis was performed of monochorionic twin pregnancies complicated by type II or type III sFGR managed and delivered at a single tertiary center from 2015 to 2023. Patients diagnosed with twin to twin transfusion syndrome, twin anemia-polycythemia sequence, or undergoing laser treatment for any indication were excluded. All twin pairs underwent fetal echocardiogram by board-certified pediatric cardiologists at our center. In cases of abnormal fetal echocardiograms, a pediatric echocardiogram was performed after birth. Clinically relevant data were obtained from electronic medical records. Right and left myocardial performance index (MPI) were calculated incorporating ejection, isovolumetric contraction, and isovolumetric relaxation times as well as combined cardiac output, cardiac hypertrophy, and tricuspid regurgitation. During the study period, 35 pregnancies complicated by type II or type III sFGR were managed by our team. Two patients were excluded as they did not undergo fetal echocardiograms as planned. The remaining 33 twin pairs underwent echocardiogram analysis at 20 weeks ± 6 days on average. Compared to the sFGR fetuses, appropriate for gestational age (AGA) fetuses were more likely to have tricuspid regurgitation (TR, 37 vs. 9%, p = 0.02), right ventricular hypertrophy (RVH, 42 vs. 9%, p = 0.003), left ventricular hypertrophy (31 vs. 3%, p = 0.006), elevated right MPI (0.36 [0.26, 0.49] vs. 0.29 [0.24, 0.35], p = 0.03), and elevated left MPI (0.32 [0.29, 0.47] vs. 0.29 [0.25, 0.35], p = 0.02). No difference was noted in combined cardiac output (534 [483, 596] vs. 522 [447, 596], p = 0.41). At birth, 55% (6/11) of AGA fetuses with abnormal fetal echocardiograms had RVH and TR compared to 25% (1/4) of sFGR fetuses. In this cohort of expectantly managed monochorionic twins complicated by type II and type III sFGR, larger twins were noted to have several findings consistent with hemodynamic changes which could reflect cardiac overload in the prenatal period. In addition, these may persist during neonatal life. Further assessment of neonatal and pediatric outcomes is needed to determine the long-term implications of these sonographic findings.