The femur length of 42mm at 29 weeks may be related to calcium deficiency, heredity and developmental abnormality, which can be dealt with by supplemental nutrition and DNA examination.
1. Calcium deficiency: under normal circumstances, at 29 weeks of pregnancy, the fetal femur length range is 5.61±0.44cm, i.e., 5.17~6.05cm. 4.2cm of fetal femur length may be caused by insufficient nutrition of the fetus and growth limitation, such as lack of calcium, etc. Pregnant women can promote the development of bones by supplementing calcium and protein-rich food.
2. Heredity: It may also be related to heredity, and DNA test is needed to judge.
3. Abnormal fetal development: Pregnant women need to pay attention to fetal movement, whether there are symptoms such as abdominal pain, vaginal bleeding, etc. If there is any abnormality, they should go to the hospital for examination in time.