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Short Femur or Humerus

 

What is a fetal soft marker?

A soft marker is a finding at the morphology (18-20 week) scan which:

·         can occur in a normal fetus

·         can occur in a fetus with Down syndrome

·         is not an abnormality

·         increases the risk for Down syndrome above your age-related risk

 

 

What does a short femur or humerus mean for my baby?

Studies have shown that some fetuses with Down syndrome have slightly shorter femur (thigh bones) and/or humerus (upper arm bones) lengths. For this reason, 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.

 

 

 Ultrasound image of femur

 

 

What happens next?

After a soft marker has been detected, the sonographer or doctor will look closely at the fetus for any other markers. After the scan, you will have the opportunity to ask questions and discuss your options with a doctor or a genetic counsellor. The significance of the finding will be explained to you. 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).

 

References

Nicolaides KH, Screening for chromosomal defects, Ultrasound Obstet Gynecol, 2003; 21: 313-21

 

Nicolaides KH & Pilu G, Diagnosis of fetal abnormalities: the 18-23 week scan, Parthenon Publishing Group, New York, 1999.

 





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