The Effect of Chorionicity on Maternal Cardiac Adaptation to Uncomplicated Twin Pregnancy: A Prospective Longitudinal Study

Objective: The objective of this study was to longitudinally evaluate maternal echocardiographic findings in uncomplicated twin gestations according to chorionicity. Methods: Healthy women with twin pregnancy were assessed with transthoracic echocardiography across the first, second, and third trimesters. Cardiac findings were compared within each group and between monochorionic (MC) and dicho-rionic (DC) pregnancies. Results: Overall, 19 MC and 48 DC uncomplicated twin pregnancies were included. In the MC group, no significant maternal haemodynamic changes were documented across gestation, with the exception of a decrease in ejection fraction. Compared to DC pregnancies, in the MC set lower cardiac output (second and third trimester, p = 0.001 and p = 0.006, respectively) and higher total vascular resistance (first trimester, p = 0.032) were observed. Regarding the diastolic function in MC twins, significantly higher values were observed for mitral E/A ratio (third trimester, p = 0.014), septal mitral E1/A1 ratio (third trimester, p = 0.030), lateral mitral E1 (second and third trimester, p = 0.014 and p = 0.029, respectively), and E1/A1 ratio (third trimester, p = 0.006). Conclusions: Maternal cardiac adaptation in twin pregnancy seems to differ significantly according to chorionicity. In particular, in MC pregnancies the impairment of diastolic function is less pronounced, presumably due to the lower circulating volume.