Objective: To investigate maternal cardiac function in twin pregnancy.
Methods: We conducted a cross-sectional study of 119 pregnant women with twin pregnancies at 10-40 weeks' gestation. Two-dimensional and M-mode echocardiography of the left ventricle was performed in the left lateral decubitus position to assess left ventricular longitudinal and transverse systolic function. The measurements were compared with those obtained from 128 women with singleton pregnancies previously reported.
Results: In twin pregnancies, compared with singletons, maternal cardiac output was greater by 20% (P <.001), because of a greater stroke volume (15%, P <.001) and heart rate (3.5%; P =.04). Furthermore, in women with twins there were greater left ventricular end-diastolic and left ventricular end-systolic dimensions, left ventricular mass (13.5%; P <.001), fractional shortening (3%; P =.04), and ejection fraction (2.5%; P =.04). Mean arterial pressure and global time to shortening in women with twins, compared with singletons, were less in the first trimester by approximately 2%, but after midpregnancy they increased progressively, so that at term the measurements were greater by 3% and 5.7%, respectively (P =.03). Conversely, long axis shortening in women with twins, compared with singletons, was greater in the first trimester by approximately 6.5%, but at term it was 3% less (P =.01). Twin pregnancies that subsequently developed preeclampsia had a hemodynamic profile similar to the rest of the twin population.
Conclusion: Twin pregnancy is characterized by an even more hyperdynamic circulation than singleton pregnancy. Left ventricle longitudinal systolic function and mean arterial pressure are more abruptly affected after 20 weeks compared with singleton pregnancies.