Generally, the fetal weight is judged through the ultrasound checklist mainly based on the biparietal diameter, femur length, head circumference, chest circumference and abdominal circumference, thus the conclusion is reached by comprehensive analysis of the fetal condition, and there are two common ways as follows: 1, computer built-in formula estimation: some ultrasound instruments can calculate with the built-in system formula based on the data of different parts measured during the examination, and the fetal weight is indicated on the ultrasound checklist. 2, formula estimation: the commonly used formula for calculating fetal weight is 1.07*BDP*BDP*BDP+0.3*AC*AC*FL, where BDP is biparietal diameter, AC is abdominal circumference and FL is femoral length, the unit is collectively cm, and the fetal weight can be roughly calculated by the data given on the ultrasound sheet. In addition, besides using ultrasound to detect the weight of the fetus, in the second trimester, the size of the fetus and the thickness of the abdominal wall can also be determined by the doctor’s palpation, so that the weight of the fetus can also be analyzed comprehensively and the growth and development of the fetus can be judged. However, because the accuracy of abdominal circumference measurement is related to the degree of obesity of the abdominal wall and subcutaneous fat of the pregnant woman, the calculation result may have a certain error. It is recommended that pregnant women should do regular maternity checkups at all stages, pay close attention to the fetal development, and if the fetus develops abnormally, further examinations can be improved under the guidance of the doctor, and targeted measures can be taken to treat the cause after it is clear.