Pregnant women usually have a 4D examination between 22-26 weeks of gestation and do not need to accumulate urine during the examination. 4D ultrasound is an imaging test that can detect obvious fetal malformations, but not all of them. The content of 4D ultrasound examination is as follows: i. Number of fetus, fetal orientation, heartbeat, etc. Amniotic fluid volume: Amniotic fluid index and maximum amniotic fluid depth can be used to show. Third, placental position, maturity and the relationship of the inner cervical opening, the number of umbilical cord and umbilical vessels, the part of the umbilical cord attached to the placenta, and the umbilical blood flow S/D ratio. Measurement of fetal growth pathways: including biparietal diameter, femur length, humerus length, etc., head circumference, abdominal circumference and head circumference/abdominal circumference ratio. V. Fetal structure: including head and neck, chest, abdomen, spine, limbs, etc. respectively.