4D ultrasound can rule out fetal abnormalities and the best time to check is 20-24 weeks of pregnancy. If the fetus has abnormalities, it will need to be rechecked after 2 weeks. During 20-24 weeks of gestation, the fetus has more developed organs and tissues, and has more space to move around more frequently. Therefore, 4D ultrasound can display the real-time dynamic images of the fetal body surface and the internal organs, and can better obtain the structural information of the fetus in all sections. Especially when there are suspected structural abnormalities of the cavernous system such as cleft lip and palate, spina bifida, congenital heart disease, etc., 4D ultrasound can clearly display them, which is more conducive to evaluation and screening and has important clinical significance for diagnosis. Although 4D ultrasound is more sensitive and accurate, it is not recommended as a routine ultrasound examination. Routine labor and delivery with 2D ultrasound is sufficient to understand the development of the fetus.