In general, the fetal femur length at 39 weeks of pregnancy is 68.1-78.7mm, so the femur length of 71mm is within the normal range, which means that the fetus is developing well and there is no need to worry too much, and it usually does not affect the normal delivery. Femur length, the length of the thigh bone, is one of the indicators of fetal growth and development, and can be accurately measured by ultrasound, which is used to reflect the length of the lower limbs of the fetus and thus determine the development of the fetus. If the test shows abnormal femur development, it may be related to many factors, such as calcium deficiency during pregnancy, congenital genetics, intrauterine growth retardation and data error during measurement. If the measurement of fetal femur length differs significantly from the standard value, it is necessary to improve the relevant tests under the guidance of the doctor to identify the cause of the abnormal fetal growth and development, so that targeted measures can be taken to deal with it. In addition, the 39th week of pregnancy is already in the late stage of pregnancy and there is a possibility of delivery at any time. If there is a decrease in fetal movement or frequent fetal movement, you should consider whether there is fetal hypoxia. In addition, pay attention to a balanced diet, replenish the nutrition required by the fetus, exercise appropriately, keep a happy mood, and if there is irregular abdominal pain, redness and other symptoms suggesting that labor may be imminent, you should be admitted to the hospital in time for delivery.