4D is four-dimensional color ultrasound, and the large ultrasound belongs to a kind of four-dimensional color ultrasound, which can be used for the detection of fetal malformations. 4D ultrasound belongs to the imaging examination, which is mainly used to diagnose heart disease, fetal malformation, but also can be used in biology, industry, and military and many other fields. When a pregnant woman undergoes a 4D ultrasound, the test is usually performed between 20 and 24 weeks of pregnancy. 4D ultrasound can detect a wide range of fetal malformations, such as cleft lip and palate for facial malformations, anencephaly and microcephaly for neurological malformations. It can also be used for malformations of the digestive system, such as visceral ectopia, intestinal atresia, etc., as well as malformations of the urinary system, such as hydronephrosis, urethral obstruction and other malformations, so the macroscopic ultrasound belongs to a kind of four-dimensional ultrasound, and the two can not be used for comparison. It is recommended that pregnant women follow the doctor’s instructions to have a four-dimensional examination during pregnancy, which can clearly see whether there are malformations in the fetus.