Femur measuring 6th percentile, scared..

28+5... We had our growth sonogram today. His anatomy scan he was 34th percentile, now he is 22 percentile due to his femur only being in the 6th percentile range while the rest of his body is measuring the same. Everything else looks great. They are sending us to a high-risk specialist Friday for reassurance with a more in-depth sonogram. This happened to anyone else? First time mom and terrified!