Four-dimensional can see men and women, but our laws prohibit the identification of the sex of the fetus, except for medical needs. Four-dimensional is short for four-dimensional color ultrasound, is based on three-dimensional medical color ultrasound imaging, plus the time, so it can display dynamic three-dimensional images, can provide a wealth of imaging information for clinical diagnosis, reduce the rate of disease diagnosis, especially in fetal ultrasound, can dynamically display the development of the face and trunk limbs of the fetus. Four-dimensional pregnancy usually 20-24 weeks for examination, this is the best time to rule out fetal malformations, and the external genitalia of the fetus in 12 weeks of gestation has been developed, at this time through the four-dimensional ultrasound can be clearly seen to men and women, but China’s laws prohibit the identification of the sex of the fetus. The purpose of the 4D ultrasound during pregnancy is mainly to rule out fetal malformations, not to see male and female, after all, the health of the fetus is the most important.