Due to the time of menopause, the standard of fetal femoral diameter can vary greatly. For women who are 24 weeks pregnant, the usual femur length is around 43 millimeters, at which point the biparietal diameter can reach 59 millimeters. At 28 weeks of pregnancy, the normal femur length is 53 millimeters, and by 34 weeks of pregnancy, the umbilical femur length can reach 66 millimeters. At 37 weeks of pregnancy, the fetal femur length is usually about 72 mm, and the pregnancy week and ultrasound results, up and down a week difference is normal.