baby's abdomen measuring big

At my 26 weeks ultrasound my baby's abdomen was measuring larger than the rest of his body. I had another growth scan yesterday at 34 weeks and my OB says his abdomen is still measuring larger. Baby is 60th percentile in all other growth but 90th percentile in abdomen. I have read this is common in moms with gestational diabetes but I don't have GD. I can't seem to find any info on what this might mean in a "normal" pregnancy. The plan is to have another scan at 38 weeks to see if measurements are more equal. Has anyone experienced this?