Level III prenatal ultrasound, also known as three-dimensional ultrasound, includes an examination of the shape of the fetus, the placenta, and the amniotic fluid, and is the primary means of examining the fetus for malformations. The three-level ultrasound examination can reconstruct the organs and tissues of fetal growth and development in a three-dimensional and dynamic way, which is used to observe whether there are any abnormalities in these tissues and ensure that the fetus is normal. It can check the function of the placenta, the amount of amniotic fluid, changes in the umbilical cord, and can also detect the pregnancy of a pregnant woman. Under normal circumstances, it is a test that pregnant women must do between 18 and 24 weeks, pregnant women should pay attention to a light diet before the examination, avoid cold, spicy and stimulating food and pay attention to warmth, the third level of prenatal ultrasound examination takes a longer time, no need to fasting. Level 3 ultrasound also has limitations, and cannot detect all abnormalities in the baby, nor can it detect the baby’s intelligence and other conditions.