Biparietal diameter is the length of the widest part of the fetus between the left and right sides of the head, and femoral length is the length of the fetal thigh bone, these two indicators can help to assess the fetal growth and development. The measurement of biparietal diameter during pregnancy is often used to observe the development of the fetus. For some women with irregular menstruation, the biparietal diameter can be measured by ultrasound to estimate the week of pregnancy, and this data can be used to help estimate the weight of the fetus in the middle of pregnancy, and in the late pregnancy to help determine whether there is a possibility of cephalopelvic disproportion and whether the delivery will be successful. Femoral length is also one of the important data for calculating fetal weight during pregnancy. As the gestational weeks increase, the value of femoral length will gradually increase, indicating that the fetal length and weight are gradually increasing. In addition to looking at the biparietal diameter and femur length, the pregnancy should be analyzed in conjunction with the fetal head circumference and abdominal circumference. If the examination only reveals a single abnormality, don’t worry too much first, first verify the gestational week, repeat the examination at an interval of 1-2 weeks, then dynamically observe the fetal growth and development, and if there is indeed an abnormality, the cause needs to be further clarified and then targeted treatment.