Short femur measurement in 6th percentile

We had a growth ultrasound at 34+3 due to concerns as I was showing borderline signs for gestational diabetes. Doctor has informed us today that all measurements seemed normal and our son was measuring in the 26th percentile for weight. One measurement was off and that was his femur in the 6 th percentile. Unfortunately they don't give us much information so I do not know all the measurements but our first ultrasound was at 24 weeks and nothing concerned the doctor then. We will be going back for another ultrasound hopefully next week.

Has anyone had any experiences with short femur measurements?  Of course we all turn to google and other sources of information that just drive us crazy. I see that it is a soft marker for down syndrome.  Any information would be very much appreciated!