Babies tummy measuring way ahead rest of measurements

AMP

Just wondered if anyone else has experienced this and the outcome in their situation. Had a growth scan at 34.4 weeks. His AC is above the 97th centile while his overall growth is on the 69th (this has dropped from the 94th at 31 weeks) I have been tested for diabetes twice and passed both. I am 5ft 1 and have a BMI of 18.3 normally so not large myself.

Anyone had a similar experience of know what a possible reasoning for this is?