Long Story of Short Femur: A Single-Center Study with Step-Wise Imaging Approach.

Purpose: To evaluate the possible outcomes of fetuses diagnosed with short femur length (FL) and to guide diagnosis through a step-wise imaging algorithm.

Methods: This was a prospective cohort study of 42 pregnancies with fetal femur length (FL) below the 5th centile for gestational age. The cases were divided into two categories of isolated short FL & non-isolated short FL and followed up to determine the etiology.

Results: There were 11 cases of non-isolated short FL with skeletal dysplasia observed in 7 and chromosomal abnormalities in 4 cases. There were 31 cases with isolated short FL in which fetal growth restriction (FGR) occurred in 14/31 (45%) cases; 13 out of 31 (42%) were constitutional (short for gestational age, SGA) whereas 4/31(13%) showed normal interval growth on follow up (false positive).

Conclusion: Short femur can be isolated or non-isolated. Short femur length can be a good predictor and early sign of FGR. Serial follow up scan of the all cases of isolated short FL is important since a majority of them are normal and not require any further intervention. Cases of non-isolated short FL require step-wise approach to differentiate into dysplasia or aneuploidy.