If a woman at about 24 weeks of pregnancy, the examination of four-dimensional ultrasound suggests that the fetus is a perpetual left superior vena cava, which means that the left anterior main vein of the fetus and the left Cuiver’s canal do not close, and the formation of drainage into the coronary sinus. If the fetal heart ultrasound suggests no other abnormalities at this point, there are usually no pathologic changes and no adverse signs or symptoms, so there is no harm. However, if there is a combination of congenital cardiac anomalies, then it may cause fetal cyanosis, as well as respiratory distress.