It is reported that children with precardiac disease account for about 8% to 12% of births in China, which means that about 120,000 to 200,000 children with precardiac disease are born every year, almost one case every three minutes, and about 20% of them are complicated or prone to early death after birth, which is one of the main causes of death of newborns and children. This places a heavy burden on families and society and causes endless suffering to the affected children. Therefore, it is necessary to carry out prenatal diagnosis of fetal congenital heart disease, which is in line with our national policy of eugenics to improve the quality of birth population and reduce the mortality rate at low age. One of the most important tools is fetal echocardiography. Early pregnancy screening for fetal congenital heart disease. Screening should be performed at 11-14 weeks of gestation. This screening should be performed primarily in fetuses with a family history of congenital heart disease, thickened posterior nuchal translucency (NT), or with chromosomal abnormalities. The two main screening methods are direct and indirect. Indirect methods include: posterior nuchal translucency measurement, venous catheter flow analysis, and tricuspid regurgitation. The direct method is the fetal echocardiogram. There are two types of fetal echocardiography: transabdominal and transvaginal. Both have advantages and disadvantages. Transabdominal fetal echocardiography is easily limited by fetal position and resolution. Transvaginal fetal echocardiography is limited by the movement of the probe and is not suitable for pregnant women (>13 weeks) whose uterus is already in pelvis. For mid-pregnancy diagnosis of fetal precocious heart disease, screening at 16 weeks of gestation is recommended for high-risk fetuses. In contrast, for routine screening, screening can be done at 18-24 weeks. High-risk fetuses are those with a family history of precocious heart disease, heart abnormalities found on delivery, abnormal fetal heart rhythm, fetal edema, thickening of the posterior nuchal translucency layer found in early pregnancy, or by chromosomal abnormalities. Screening at 18-24 weeks is also recommended for fetuses with metabolic diseases such as diabetes, history of teratogenic drug exposure, intrauterine infections, autoimmune diseases, familial syndromes, extracardiac malformations or in vitro fertilization in this group.