4D is also known as 4D ultrasound, and 4D ultrasound can show malformations of the sex organs. Four-dimensional color ultrasound can usually show fetal sex organ malformation, this is also a more important examination of the detection of malformations during pregnancy. The examination can observe the development of various organs on the fetal body surface, as well as the state of the fetus in the mother’s body, such as whether the fetus has cleft lip and palate, spina bifida, malformation of the reproductive organs, underdevelopment of internal organs, and abnormalities of the surface structure of the limbs or torso. Generally, 4D ultrasound can be done in 20-24 weeks of pregnancy, this period of amniotic fluid conditions and moderate size of the fetus, a clear field of vision, so the mid-pregnancy is the best time to screen the development of the fetus with or without malformations. Pregnant women can drink some milk or eat some fruit 30 minutes before the 4D ultrasound, which is conducive to fetal activity and facilitates an all-round examination. It is recommended to follow the doctor’s instructions for regular checkups during pregnancy, and to actively cooperate with the doctor if there are any abnormalities.