Congenital heart disease in monozygotic twins

Abstract Congenital heart defects (CHDs) represent the most common human birth defect, having a birth prevalence of 7–9 per 1000 singleton live births. CHDs are more common in twin pregnancies with a prevalence of 13 in 1000 total births. Monochorionic (MC) twins are even at higher risk (20 in 1000 total births) compared to dichorionic twins (11 in 1000 total births). In MC twins, all types of congenital heart defects are found. Furthermore, in this specific group of twins the development of acquired structural heart disease can be encountered in association with twin–twin transfusion syndrome.