Four-dimensional is better than three-dimensional in real-time, dynamic, multi-angle and multi-directional observation of fetal development. At the same time, the inspection time only takes about 20 minutes. It is very convenient to make an appointment in advance, make an appointment in advance and be on call. In addition, four-dimensional color Doppler ultrasound can image the fetal surface, and congenital malformations such as cleft lip and palate, limb development deformity, meningocele, spina bifida and gastroschisis can be more clearly detected. The diagnostic data of four-dimensional color Doppler ultrasound is also beneficial to the doctor's judgment.