Prenatal ultrasound is divided into Level I, Level II, and Level III, all of which are performed in two dimensions. Both 2D and 4D are performed using ultrasound, not radiation, and there is no radiation to the fetus. However, when performing obstetric ultrasound examinations, one should always be aware of safety. Ultrasound, as a physical energy, is bound to have safety dose issues, especially in early pregnancy examinations where special attention should be paid. If ultrasound damages only a few cells in most organs of the body it is insignificant, but for human germ cells and early embryonic cells in their developmental stage, even a few cells cannot be tolerated. The issue of the safe threshold dose for ultrasound has not yet been rigorously proven scientifically. The principle of using the minimum dose should be adhered to when performing obstetric examinations, and all fetal ultrasound examinations that are not diagnostically relevant should be rejected, including commercial ones and those performed solely to check the sex of the fetus. The examinations should be minimized as much as possible during pregnancy, and if they are to be performed, they should be observed for as short a time as possible, and should not be performed for a long time during early pregnancy, 3-5 minutes at most, and especially for shorter periods of time for fetal eye irradiation. Nowadays, all pregnant women want to take 4D photos for their babies in their bellies to keep a souvenir, but the examination with 4D ultrasound is more time-consuming and laborious, and the time spent in the fetal face is longer, so we should pay more attention to its possible biological effects and potential dangers. Therefore, it is not necessary for every pregnant woman to have a 4D ultrasound if there is no special need for it.