3D and 4D ultrasound are similar in terms of actual deformity detection, ultrasound is just a formality, what is more important is the level of the ultrasound doctor. Generally speaking, three-dimensional ultrasound has already had sufficient effect of detecting malformations, three-dimensional and four-dimensional detector effect is similar, four-dimensional is only on the basis of three-dimensional, able to retain the video image, able to play back. Three-dimensional ultrasound results is a three-dimensional static picture, can measure all parts of the fetus, including fetal organs and limbs and bones, four-dimensional ultrasound results is a dynamic video, can be more intuitive and clear to see the movement of the fetus, from a multi-directional, multi-angle observation of fetal growth and development. Since the observer is the ultrasound doctor, the doctor’s level directly determines the effect of the detector. Due to the complexity of pregnancy, it is recommended to consult with the appropriate professional doctors in the hospital and choose the appropriate examination program under the advice of the professional doctors.