Fetal congenital heart disease is referred to as fetal congenital heart disease. It is reported that congenital heart disease accounts for 8% to 12% of babies born in China, which means that 120,000 to 200,000 children with congenital heart disease are born in China every year, among which the complicated ones, those whose current treatments are not yet able to achieve a good therapeutic effect, or those who are prone to early postnatal deaths account for about 20%+, and they are one of the major causes of death in newborns and childhood. According to statistics, about 6 out of every 1000 newborns suffer from congenital heart disease. According to the birth rate and the incidence of congenital heart disease, it is estimated that there are 150,000 sick children born in China every year. Congenital heart disease is a cruel “killer” that jeopardizes the health and lives of children and adults. Echocardiography is a non-invasive, safe and reliable prenatal diagnosis of complex congenital heart malformations, cardiac tumors, cardiomyopathies, arrhythmias, fetal echocardiography is an important part of prenatal ultrasound monitoring to predict the health of the fetus, which is in line with our country’s eugenics policy to improve the quality of the population at birth and to reduce the mortality rate of the lower age. Classification of fetal cardiac malformations 1, lethal malformations: hypoplastic left heart syndrome, pulmonary artery atresia, tricuspid atresia, single ventricle, single atrium, two-chambered heart, right heart hypoplasia, endocardial cushion defects, multiple malformations (tetralogy of Fallot, etc.). Non-fatal malformations: atrial septal defects, ventricular septal defects, ventricular defects combined with atrial defects, right heart, coarctation of the ductus arteriosus, and so on. The perinatal mortality rate of lethal cardiac malformations is high, the cost of surgical treatment is high, the outcome is poor, and the average life expectancy is much lower than that of the normal population. The purpose of fetal cardiac ultrasonography is to provide prenatal diagnosis of these complex, difficult-to-treat, and easy-to-birth-death fetal cardiac abnormalities, so as to provide the clinic with timely and correct scientific diagnostic basis, and enable timely diagnosis and treatment of the fetus before and after birth. Indications Birth defects are caused by both genetic and environmental factors. The main causes of fetal heart malformation are related to genetic factors, pathogenic microorganisms, chemical and physical factors. Fetal congenital heart disease risk factors are both maternal and fetal: (a) maternal: 1, maternal diabetes mellitus, connective tissue disease (such as systemic lupus erythematosus), chronic alcoholism. 2, early pregnancy with viral infections (such as lupus erythematosus). 2, early pregnancy viral infections, colds, high fever history, history of drug use (amphetamine, dalentine, potassium chloride, trimethoprim, etc.). 3.Early pregnancy contact with radiation, gon compounds, paints, pesticides, hair dyes or taking anticancer drugs, chemical agents and so on. 4, infected viruses: rubella virus (early pregnancy infection incidence rate of 90%, 25% in the middle), cytomegalovirus incidence rate of 1 to 2%, toxoplasmosis incidence rate of 1 to 2%, human microvirus B19 intrauterine infection of fetal mortality rate of 9%. 5.Pregnant women of advanced age (age greater than 35 years), history of abnormal pregnancy, abortion, induced abortion, congenital heart disease birth history, and so on. 6, parents or siblings have congenital heart disease and family history of heart disease such as hypertrophic cardiomyopathy. （Fetal factors: 1. Fetus combined with other organ malformations: such as hydrocephalus, abdominal wall cleft. 2, Chromosomal abnormalities. Fetal arrhythmias: including bradycardia (less than 120 beats/min), tachycardia (more than 200 beats/min) and arrhythmia. 4, Fetal edema: including fetal subcutaneous and body cavity (chest and abdominal wall) fluid accumulation, pericardial effusion. 5.Amniotic fluid abnormality: too much amniotic fluid or too little amniotic fluid. 6, Fetal intrauterine growth retardation. However, it has been reported that 1/3 of fetal heart disease is not accompanied by high risk factors of congenital heart disease, if only the high-risk factors of the fetus to do echocardiography will result in 1/3 of the fetal heart disease missed, so it is recommended that as far as possible prenatal echocardiography of each fetus to do once. Optimal period The embryo develops to the second week and begins to form primitive blood vessels, the third week forms the primitive cardiovascular system and has the blood circulation, the 7th~8th week the atrium and ventricle are formed, the fetal heart structure is basically completed. Therefore, in this period of time the fetus is subjected to any external stimuli will affect the fetal cardiovascular development. However, early fetal heart is small, the section is not clear; late fetal bone development behind the influence of acoustic shadow and the influence of the fetal position will lead to the influence of the fetal heart detection. 20 weeks to 28 weeks is the best time for fetal echocardiography detection.