The difference between the 30-week microdiagnostic examination and the four-dimensional ultrasound is mainly reflected in the examination mode, examination time, examination items, etc., which need to be specifically analyzed. 1. Inspection method: 30 weeks of micro-anomaly examination uses two-dimensional color ultrasound for examination, and four-dimensional uses four-dimensional color ultrasound for more comprehensive observation. 2. Examination time: micro-anomaly examination is carried out in 30-32 weeks of pregnancy, and four-dimensional ultrasound examination is carried out in 20-28 weeks of pregnancy. 3. Examination items: Micro-anomaly examination is mainly to screen whether the fetal cranium, spine, kidneys, liver and other structural malformations, amniotic fluid content, placenta guard position and maturity is normal. Four-dimensional ultrasound can show three-dimensional images of the fetus in the body, which is more conducive to the discovery of harelip, spina bifida, cardiac anomalies, etc., and more detailed observation. It is recommended that pregnant women undergo regular pregnancy tests, under the guidance of the doctor. Pregnant women should pay attention to a moderate amount of exercise before the detoxification and before the 4D, which will help the baby’s movement in the womb and make the observation more clear.