Femur length at 29 weeks of pregnancy is less than three weeks of normal gestational weeks to retest the femur length, in addition to monitoring other indicators of fetal comprehensive assessment of fetal development, if necessary, amniocentesis to determine whether there is the possibility of fetal chromosomal malformations. If the femur length is small, there may be measurement error, so it is recommended to retest the femur length, which is usually small within two weeks. Combined with other fetal indicators, such as biparietal diameter, head circumference, abdominal circumference and humerus length to assess fetal development, if they are all small, it is necessary to pay attention to the need for further examination, such as amniocentesis to determine whether there is the possibility of fetal chromosomal malformations. Therefore, during pregnancy, we should pay attention to rest, reasonable nutrition, avoid exposure to radiation, avoid taking any medication in early pregnancy, take regular checkups during pregnancy to assess fetal growth and development, and go to the hospital as soon as possible for checkups if there is any discomfort.