EP14.11: Maternal cardiovascular dynamics in twin pregnancies complicated by Twin–twin transfusion syndrome

Twin pregnancies affect maternal circulation by increased circulating blood volume and an enlarged uterus due to excess amniotic fluid. However, it has not been clarified how Twin–twin transfusion syndrome (TTTS) may affect on maternal circulation. This study aimed to examine changes in maternal circulation at the onset of TTTS. This cohort study was conducted at Toho University Omori Medical Center from October 2022 to September 2023. The patients were divided into three groups: singleton pregnancy group (singleton group), uncomplicated mono-chorionic diaphragmatic twin pregnancies (nMD group), and TTTS cases (TTTS group). We analysed prospectively collected data by echocardiography performed to evaluate left ventricular function: left ventricular contractility, diastolic performance, and IVC diameter. This study was approved by the Ethics Committee of Toho University Medical Center. During the study period, there were 31 cases in the singleton group, 17 cases in the nMD group, and 18 cases in the TTTS group. Left ventricular end-diastolic volume (EDV) and end-systolic volume (ESV) were significantly smaller in the TTTS group than in the nMD group[EDV: 86.4 ± 29.4mL nMD group vs 65.3 ± 30.2mL TTTS group; p = 0.045, ESV: 23.9 ± 9.2mL nMD group vs 13.3 ± 8.4mL TTTS group; p = 0.001], and no significant difference between the TTTS group and the singleton group. Left ventricular ejection fraction (EF) was significantly higher in the TTTS group than in the nMD group [EF: 72.2 ± 6.4% nMD group vs. 80.1 ± 5.9% TTTS group; p = 0.001], and no significant difference between the TTTS group and the singleton group. Heart rate was significantly higher in the TTTS group than in the other two groups. Cardiac output (CO) was similar in all three groups. The results suggest that an MD twin pregnancy with TTTS might decrease circulating blood volume because of the associated increase in vascular permeability. Maternal cardiac function may be adapting to compensate for CO in cases of TTTS.