This study showed that the maternal heart was at more stress during a twin pregnancy. This could be linked with the higher rate of blood pressure and heart problems that mums with twin, compared to singleton, pregnancies have. Close monitoring is needed in these pregnancies with focus on maternal cardiovascular system.
Reference: Kametas NA, McAuliffe F, Krampl E, Chambers J, Nicolaides KH. Maternal cardiac function in twin pregnancy. Obstetrics & Gynecology. 2003 Oct 1;102(4):806-15.