Fetal BPD, HC, AC, FL, HL are the codes on the checklist of ultrasound examination during pregnancy, which represent different indicators, i.e. fetal biparietal diameter, head circumference, abdominal circumference, femur length and humerus length, etc. They are important indicators to determine the fetal growth and development and whether the delivery can be carried out smoothly. The specific values are related to the month of pregnancy and should be judged by the doctor after the examination. The corresponding meanings and uses of each indicator are as follows: 1. BPD: refers to the fetal biparietal diameter, which is the length between the widest parts of the left and right sides of the fetal head. The fetal brain development can be judged by this value; in addition, if the head circumference is too large, there may be hydrocephalus and other lesions, and if the head circumference is too small, there may be microcephaly; 3.AC: refers to the fetal abdominal circumference, which is the length of the fetal abdomen for one week, and the fetal size can be judged by the fetal abdominal circumference to a certain extent; 4.FL: refers to the fetal femur length, which is the length of the fetal legs, and the fetal height and weight can be judged by this value to a certain extent, and the fetal age can be estimated; 5.HL HL: refers to the length of the fetal humerus, which is the length of the fetal arm, and can also be used to estimate the fetal height, weight and other indicators as well as the gestational age.