A femur length of 19mm at 17 weeks of gestation is slightly short and needs to be reviewed regularly as prescribed by your doctor. The femur length at 17 weeks of pregnancy should be around 25mm. Short femur length can be caused by insufficient nutrition during pregnancy, calcium deficiency or abnormal fetal bone development. Calcium deficiency Normally, after 12 weeks of pregnancy, calcium demand is relatively large, pregnant women are prone to lack, so generally from 12 weeks to supplement calcium tablets, and then also eat some eggs, lean meat, shrimp, fish and other food supplements. Attention should be paid to more sunshine also helps vitamin D binding, in order to promote the absorption of calcium. Abnormal bone development is usually caused by chromosomal abnormalities or fetal growth restriction in the uterine cavity. If the fetal femur length is persistently short on late examination, further investigation of the chromosomes, etc., should be done to determine the cause.