In general, they are divided into the following categories: 1) congenital heart disease: the incidence is high and most of them can be diagnosed prenatally; 2) digestive system malformations: including atresia and stenosis at all stages of the digestive tract and functional intestinal obstruction due to congenital neurodevelopmental abnormalities; 3) urinary system malformations: the incidence of hydronephrosis due to abnormal kidney development is high and can be examined by ultrasound prenatally; 4) skeletal system malformations and neurological malformations, etc.