Hi, Thank you for choosing Healthcaremagic. The detection of a fetus with a bone length which measures shorter than the normal range will increase the risk of Down syndrome. It is acknowledged however that the “normal” range may differ depending on ancestry or parental stature (height). Not all fetuses with short femur or humerus measurements will have Down syndrome. If the presence of short femur and/or humerus measurements adjusts your risk of a chromosome abnormality into the high risk category, or, if you feel that the presence of this marker is likely to cause you ongoing concern, amniocentesis may be offered to you. This test examines the baby’s chromosomes, but has an associated risk of miscarriage (1:200). Please ask if you have more questions. If you are satisfied, please make sure that your ACCEPT my answer so that I receive credit. Good luck!!