Biparietal diameter of 84mm and femur length of 56mm at 30 weeks of pregnancy are within the normal range. Biparietal diameter (BPD), also known as the biparietal diameter of the fetal head, is the length of the widest part of the fetal head between the right and left sides; and femur length is the length of the thigh bone. In general, the normal range of fetal BPD in 30 weeks of pregnancy is 7.83 sh 0.62cm, while the normal range of femur length is 5.77 sh 0.47cm, so the BPD of 84mm and the femur length of 56mm in 30 weeks of pregnancy are generally normal. The 30-week pregnancy examination is mainly an ultrasound examination, which can monitor whether the fetus develops to the normal range, of which the biparietal diameter and femur length are important monitoring indicators, which can understand whether the development of the fetus is too big or too small, and it is generally normal to fluctuate within the normal range.