Birth defects are structural and functional abnormalities that occur during the development of an embryo or fetus. With the gradual eradication of infectious and contagious diseases by human control, birth defects have become an important cause of death or disability in infants and children, seriously affecting the quality of the birth population and gradually becoming an important issue of public health and social concern. Congenital malformations are birth defects characterized by morphological and structural abnormalities, accounting for about 60%-70% of birth defects, and are the most important type of birth defects. The incidence of fetal congenital malformations in China is about 13%, and there are various types of fetal congenital malformations, the following are classified according to each system 1, digestive system: such as harelip, cleft palate, esophageal atresia, megacolon, rectovaginal fistula, rectourethral fistula, anus, etc. 2. Respiratory system: septal hernia, tracheoesophageal fistula, pulmonary hypoplasia, pulmonary cysts, etc. 3.Circulatory system: congenital heart disease, atrial and ventricular septal defect, right-sided heart, tetralogy of Fallot, aortic valve atresia, etc. 4.Neurological system: congenital stupidity, anencephaly, hydrocephalus, underdeveloped brain. 5.Skeletal system: craniosynostosis, hypoplasia of the lower palate, thoracic deformity, spina bifida, multiple ribs, flexural defects, osteogenesis imperfecta, etc. 6.Genitourinary system: hypospadias, cryptorchidism, testicular syringomyelia, absence of vagina, renal agenesis, etc. 7.Skin: preauricular redundancy, hemangioma, large nevus, neck webbing, skin defect, etc. 8.Limbs: polydactyly, polydactyly, clubfoot, finger deformity, foot deformity, bilateral arm deficiency, etc. 9.Ears, eyes and nose: small ears, no ears, atresia of the external ear canal, no ophthalmoplegia, small eye fissures, no nostrils, etc. 10.Other: hiatal hernia, umbilical bulge, abdominal muscle defect, etc. The causes of fetal malformation congenital malformation can be caused by two factors: one is environmental factors; the other is genetic factors. It is generally believed that most congenital malformations are caused by multiple factors. Embryonic development can be divided into three periods: the first period is the predifferentiation of cells and tissues; the second period is the differentiation of cells and tissues; and the third period is the differentiation of organs and functions. Environmental teratogenic factors are generally most likely to cause malformations in the second and early third stages. During the development of cell and tissue differentiation in the second stage, the synthesis of genes and enzymes under the control of genes plays an important role, which makes all cells and tissues form the progenitor of each organ according to the genetic law, and further differentiate each organ with its own function. The evolution of this differentiation is extremely delicate and complex, and a disturbance in one of them can cause malformations to occur. Intrauterine diagnosis of fetal malformations With the development of recent diagnostic techniques, the methods of intrauterine diagnosis of congenital malformations are gradually increasing. The following tests should be considered for pregnant women over 35 years old; one of the couples is an autosomal translocation carrier; a carrier of metabolic abnormal disease; or a child with malformation. 1, B ultrasound: ultrasound examination is the preferred technology for prenatal imaging because of its low cost, high safety and accurate real-time imaging. With the development of science and technology and the continuous improvement of medical level, ultrasound examination has not only been a part of the routine examination of pregnant women, but also its diagnostic accuracy has been greatly improved, especially in the diagnosis of fetal malformations, which has become an important basis for prenatal diagnosis. MRI: MRI as an intrauterine diagnostic imaging method has the advantages of non-invasive, non-radiation damage, multi-planar imaging, large imaging range, discriminative tissue characteristics, good soft tissue contrast, high spatial resolution, image quality is not affected by gas and bone, so it can obtain high definition images of the fetus and pregnant women, and can provide more imaging information other than ultrasonography. 3. X-ray examination: X-ray examination is valuable, even the best, when the developmental abnormalities of the skeletal system and the suspected developmental abnormalities of the gastrointestinal tract are present, and can determine bipartite or polypartite malformations, anencephaly, hydrocephalus, missing limbs and other malformations. The fetal liver produces AFP in the 6th week of gestation, which is contained in both maternal blood and amniotic fluid, and it is excreted in urine in normal fetal amniotic fluid and degraded by swallowing and digestion. In fetal anomalies such as neural tube defects, AFP is leaked from blood and cerebrospinal fluid, which may increase the AFP in amniotic fluid; umbilical hernia and ventral fissure malformations increase AFP due to exposure of bulging internal vessels and leakage of fetal serum components into the amniotic fluid. The AFP in amniotic fluid can be increased in fetuses with chromosomal abnormalities (45, XO) and congenital nephropathy. AFP can be measured to help diagnose these abnormalities. 5. Amniocentesis: It is a method to confirm the diagnosis by using the affinity of fetal lipoprotein and oil-based contrast agent on the fetal surface. Using this method, the fetus can show a clear shape. Commonly used contrast agents are panthorpha and morjot. After a few hours, the contrast agent spreads and attaches to the fetal body surface, and the photos can show the abnormality. 6. Biochemical examination: (1) Determination of adrenal steroids in amniotic fluid: Fetuses with adrenal syndrome have higher levels of ketosteroids and progesterone glycol in the amniotic fluid. Their levels are reduced in anencephaly and congenital adrenal insufficiency. (2) Measurement of estriol (E3) in amniotic fluid: E3 is significantly lower in anencephalic fetuses. 7. Hysteroscopy to examine the fetus: The placenta and fetal position are first determined by ultrasonography, and then an examination mirror is placed under local anesthesia, with which fetal malformations can be observed; fetal skin biopsy can also be taken. 8, amniotic fluid cell culture after karyotype analysis, combined with the apparent band can determine the chromosomal aberrations caused by malformations of the fetus. 9. Early chorionic villus cell culture and chromosome analysis are meaningful for early diagnosis of certain genetic diseases and congenital malformations. 10. Determination of enzyme activity in amniotic fluid and identification of enzyme variants can detect inborn metabolic abnormalities and certain congenital malformations. 11. The new generation of microchip technology, peripheral plasma free DNA detection technology of pregnant women and new generation of high throughput sequencing technology: make the development of intrauterine diagnosis non-invasive and molecular trend. Prenatal intervention of fetal anomalies Advanced technologies allow many previously undetectable fetal anomalies to be diagnosed and detected prenatally. From the above statements, it is clear that there are many different types of fetal malformations. Although we have improved the diagnosis of fetal anomalies, the proper management of them, whether to terminate the pregnancy or to choose to continue it, is an important issue facing obstetricians and pediatricians as well as ultrasonographers today. The management of fetal malformations can be divided into the following 3 categories according to the degree of fetal malformation, whether it is curable or not and the near and long-term prognosis. 1. Termination of pregnancy: For fetal diseases that are lethal, termination of pregnancy is recommended after confirmation and signature by 3 or more specialists of different specialties. The six lethal malformations of mid- to late-term pregnancy, as defined by the Ministry of Health’s Regulations on Prenatal Diagnostic Techniques, include anencephaly, brain bulge, open spina bifida, thoracoabdominal wall defects (including ectopic heart, anterior mediastinal defects, sternal defects, etc., mainly combined with congenital heart diseases such as Tetralogy of Fallot and endocardial defects), single-chamber heart, and lethal chondrodysplasia. 2. Continuation of pregnancy: If the perinatal infant is expected to survive after birth and has a good prognosis after timely surgery, it is recommended to continue the pregnancy and to inform the prognosis of the perinatal infant and the process of neonatal consultation. In the article “The value of prenatal multidisciplinary consultation model on the diagnosis and treatment of fetal structural malformations” published by Shen Chun et al. in Chinese Journal of Perinatology, among 2622 cases of fetal structural malformations, 935 cases were induced, and the remaining 1687 cases continued pregnancy. Among various malformations, the malformation with the highest percentage of continued pregnancy was sacrococcygeal teratoma, followed by abdominal occupancy, urinary system malformation, and digestive system malformation. 3. Perinatal treatment: if timely intervention can improve the prognosis of the perinatal infant, develop treatment plans for the gestational and neonatal periods, and complete perinatal management (including treatment during pregnancy, management during extra-uterine delivery, timely transfer and neonatal surgery, etc.) together with the corresponding specialties. The significance of prenatal multidisciplinary consultation is to standardize perinatal management and postnatal treatment in order to improve perinatal survival rate and quality of survival. Under the traditional model, prenatal consultation for fetal structural malformations is mainly done by obstetricians, and the assessment of prognosis and perinatal management may be incomplete. In contrast, a multidisciplinary prenatal consultation model involving all relevant disciplines can provide a comprehensive review, and in addition to prenatal consultation, treatment and follow-up plans can be developed to appropriately manage various fetal and neonatal diseases and follow up on disease regression.