Femurs <5th percentile at 28 weeks

At my 20 week scan baby measured perfectly in 50th percentile overall.

Just had my 28 week scan, baby is 45th percentile, but femurs are only 4th percentile.

Everything else is perfect.

I am so concerned and upset that there might be something wrong. They have booked me in with a consultant in 2 weeks time for another full body check and measurements.

Does anyone else have experience of this, with femurs below the 5th percentile, but rest of body growing fine?