Growth scans are notoriously inaccurate towards the end, especially if baby is head down. It's one of the reasons I won't budge on an ELCS - even if they say baby is smaller than DD I won't believe them or worry any less. They predicted her to be between 7 & 8lbs so cancelled my planned induction. She was over 10lbs.
My last response was a bit flippant @gemmajen - I guess I was trying to say that bumps come in a range of shapes and sizes! Fundal measurement really isn't accurate so don't let it make you feel like you are particularly massive (or not!). If they measured me in the morning then again at night, I'm sure they would get different results. It's just one of lots of indicators. I've never really understood it because it doesn't take into account the shape of your body/amount of fat on your tummy.
Plus, someone has to the at the top and bottom of the percentile chart!