Growth check @ 37.2 wks

Just had an ultrasound last night and told the baby was 7lbs4oz. Anyone know how accurate? 
My OB wants to watch to make sure the baby doesn't get too big as my last was c-section. The plan was to try to have this baby naturally (EDD 27th) and planned c-section the week after. I'm guessing my OB will want to re-book everything at this rate!