Biparietal diameter and femoral length are both parameters used in clinical monitoring of fetal growth and development. Biparietal diameter (BPD) is the length of the widest part of the fetus between the left and right sides of the head, also known as the “large transverse head diameter”, which is used to reflect the size of the fetal head, to estimate the maturity of fetal development, and to measure the proportionality of the estimated head and pelvis. After 36 weeks of pregnancy, the growth rate of fetal biparietal diameter decreases and increases by about 0.1cm per week, and the fetal biparietal diameter is about 9cm at 37 weeks, and should reach 9.3cm or more at full term. Initially, BPD is often used to predict the due date, and after the middle term, it is often necessary to measure this data as well when presuming the fetal weight. Femur length is the length of the fetal thigh bone, which can be accurately measured by abdominal ultrasound and is often used as an indicator to monitor fetal growth and development. 37 weeks of fetal femur length is around 7 cm and increases as the gestational weeks increase. The average increase in femur length is 0.21cm per week, and after 36 weeks the growth rate slows down to 0.17cm per week, and the femur length of a full-term fetus can reach 7.6cm. Combining the biparietal diameter and femur length can reflect the fetal growth more accurately.