The former refers to a type of prenatal ultrasonography, and the latter is two imaging modalities used in prenatal ultrasonography, and currently a considerable number of pregnant women and their families are prone to confuse the two. There are four types of prenatal ultrasound examination regulated by the prenatal diagnosis expert group of the Ministry of Health, namely: (1) early pregnancy ultrasound examination. (2) Routine ultrasonography in middle and late pregnancy. (3) Systematic ultrasonography in mid- to late-term pregnancy. (4) Targeted ultrasound. Each type of ultrasound examination is aimed at different conditions of pregnant women, and the requirements of the examination are also different. Among them, system ultrasonography in late pregnancy is mainly for screening fetal structural malformations, which is also commonly known as “teratology examination”, and this type of examination has higher requirements, which requires strict requirements on ultrasonographers, equipment, time required for examination, examination content and size of pregnancy week at the time of examination. This type of ultrasound examination is recommended to be performed in hospitals qualified for prenatal screening or prenatal diagnosis, so as to improve the detection rate of fetal malformations, reduce the birth of seriously defective fetuses and improve the quality of our birth population through this system of fetal ultrasound examination. Healthcare institutions that are not qualified to provide prenatal diagnostic technology services should issue an ultrasound report when they find suspicious cases during routine prenatal ultrasound examinations, and must also refer suspicious cases to healthcare institutions that carry out prenatal diagnostic technology. Many members of the public mistake this kind of examination for 3D 4D ultrasound examination. The 3D-4D is two stereoscopic and stereo dynamic imaging modalities of ultrasound, which can be used in any of the above four types of ultrasound examinations, and also in gynecological uterine examinations. 2D ultrasound is the basis of 3D 4D ultrasound, based on which 3D 4D ultrasound can provide more diagnostic information, such as for surface imaging of the fetus, such as taking pictures, etc. Certain planes that cannot be shown by 2D imaging can be obtained by 3D imaging, which can be helpful for diagnosis. However, 3D 4D ultrasound has higher requirements for the position of the fetus in the uterus, the amount of amniotic fluid and the thickness of the abdominal wall of the pregnant woman, so the main diagnostic work is still done by 2D ultrasound.