At 17 weeks, the biparietal diameter is between 3.1-4.2cm, with an average value of 3.9cm, and the femur length is between 1.8-2.6cm, with an average value of 2.4cm, and any abnormalities require timely medical treatment. The 17-week fetus is in the middle of pregnancy, the fetus is still growing and developing, due to the individual differences in fetal development, it is generally considered that the biparietal diameter and femur length within the range of two standard deviations above and below the standard value are normal, too high or too low are abnormal, and the cause needs to be clarified in a timely manner. If the fetal biparietal diameter and femur length at 17 weeks are lower than the lower limit of the normal level of the same gestation period, it should be clarified whether there is an error in the calculation of gestational weeks, and at the same time, exclude whether there is intrauterine developmental delay and other conditions; if the fetal biparietal diameter and femur length are higher than the upper limit of normal, in addition to checking the week of gestation, it should be clarified whether the pregnant woman is suffering from gestational diabetes mellitus, which leads to overnutrition of the fetus. When abnormalities occur, treatment should be carried out under the guidance of specialized physicians to avoid leading to the condition and adverse pregnancy outcomes.