Single ventricle is the heart chamber through the two atrioventricular valve or common atrioventricular valve at the same time to receive blood from two atria, leading to fetal single ventricle the main reasons are: fetal single ventricle is a developmental abnormality, affecting it a multitude of factors, the most critical with the differentiation of the tricuspid layer of the embryonic chromosomal abnormalities; may be the immune factors, genetic factors and congenital factors of the causes related. It may also be related to viral infections in early pregnancy and the poor physical condition of the pregnant woman; it may also be related to the adverse environment during pregnancy, such as radiation and excessive amniotic fluid.