The main difference between 2D and 3D ultrasound is that 3D ultrasound technology is based on 2D ultrasound, that is, 2D ultrasound is the basis of 3D ultrasound, while 3D ultrasound contains all the functions of 2D ultrasound. The ultrasound image formed by 2D ultrasound is a two-dimensional flat image, while the ultrasound image formed by 3D ultrasound is three-dimensional. There is no major difference in function between 2D and 3D ultrasound when it comes to general disease examination. In prenatal examination, 2D ultrasound can only perform general examination of the fetus, while 3D ultrasound can be used to perform teratology examination, such as congenital fetal harelip, through 3D images.