Level 3 ultrasound is also known as 3D ultrasound. Three-dimensional color ultrasound surface presented in obstetric examination, not only can observe the process of fetal growth, but also can check the placenta, amniotic fluid and umbilical cord changes, more importantly, can be used as the main means of diagnosis of fetal malformation. Three-dimensional color ultrasound belongs to a kind of color ultrasound, three-dimensional color ultrasound is three-dimensional dynamic display. The main advantage of color ultrasound in obstetrics and gynecology is that it can be used to identify benign tumors, umbilical cord diseases, other diseases including fetal congenital heart disease, as well as the evaluation of the function of the placenta, and it has a better auxiliary diagnostic value for trophoblastic diseases, and it can also be used to make diagnosis of infertility and pelvic varicose veins which are difficult to be diagnosed under the black and white color ultrasound by the observation of the blood flow spectroscopy.