There is no definite cause for fetal left ventricular cyst, but it may be related to viral infection, radiation and chemical pollutants in the uterus of the pregnant woman. 1. Viral infection: During pregnancy, if the pregnant woman’s body has low resistance and immunity, she may be infected by pathogens such as rubella virus and cytomegalovirus, which may lead to fetal left ventricular cyst. 2. Stimulation of other factors: If the pregnant woman is exposed to excessive radiation or long-term exposure to chemical pollutants, it may affect the normal growth and development of the child, leading to the occurrence of fetal left-sided ventricular cysts. Since the left ventricular cyst may affect the development of the fetus as well as other malformations, it is recommended to consult a doctor for prenatal diagnosis once it is detected and improve the relevant examinations under the doctor’s guidance.