Femur length grows gradually with fetal growth and development, with different standards for different weeks of gestation and also with individual fetal differences. In general, the normal values of femur length are: 16 weeks, 2.1-2.4cm. 17 weeks, 2.5-2.7cm. 18 weeks, 2.8-3.00cm. 19 weeks, 3.1-3.3cm. 20 weeks, 3.4-3.5cm. 21 weeks, 3.6-3.8cm. 22 weeks, 3.9-4.1cm. 23 weeks, 4.2-4.3cm. 24 weeks, 4.4-4.6cm. 25 weeks, 4.7-4.3cm. Twenty-four weeks, 4.4-4.6 cm. twenty-five weeks, 4.7-4.8 cm. twenty-six weeks, 4.9-5.0 cm. twenty-seven weeks, 5.1-5.3 cm. twenty-eight weeks, 5.35 soil 0.55 cm. twenty-nine weeks, 5.61 soil 0.55 cm. thirty weeks, 5.77 soil 0.47 cm. thirty-one weeks, 6.03 soil 0.38 cm. thirty-two weeks, 6.43 soil 0.38 cm. thirty-two weeks, 6.43 soil 0.38 cm. Thirty-three weeks, 6.32 soil 0.43cm. Thirty-four weeks, 6.71 soil 0.45cm. Thirty-five weeks, 6.95 soil 0.47cm. Thirty-six weeks, 7.10 soil 0.52cm. Thirty-seven weeks, 7.20 soil 0.43cm. Thirty-eight weeks, 7.34 soil 0.53cm. Thirty-nine weeks, 7.40 soil 0.53cm. Thirty-nine weeks, 7.40 soil 0.53 cm.