i think the way baby was positioned (head down, but hands and feet in his/her face - all scrunched up in a ball) may have something to do with it being off. The tech commented that s/he had a big belly, but if you're all scrunched up, then how accurate is that measurement?
The doctor i saw was a resident as my OB was away. To be fair,she wasn't pushing a c section, but just saying it was something to keep in mind. She may have also been bringing it up because of my placenta. My OB is not concerned with it (other than putting me on pelvic rest - poor DH) and has already told me he'd let me labour with it being the way it is (2cm away from cervix, currently) She also said that the measurements are often wrong, and that babies can measure in the 95th percentile one ultrasound, and then 4 weeks later be in the "normal" range. Baby hasn't measured way ahead in any of my other ultrasounds.
My sister (who is a twig...a tall twig) had a 9lb 7oz baby naturally. i'm hoping LO doesn't top that!