I had several scans at the end of each of my pregnancies due to my fundal height measuring small (I think it was between 2 -4 cm smaller than expected). Each time the scan actually estimated very large babies - the truth was somewhere in between. The first pregnancy i was really worried (first with the small measurement and then the much larger scan estimate!!) but with the second pregnancy I decided it was just the way I must carry, although I still had the scans to make sure all was looking ok.
DS1 was induced at 37.3 weeks and was 7 pound 6 (3.2 kgs), 2 days earlier the scan estimate had been over 9 pound
DS2 was born at 38.6 weeks and was 8 pound 6 (3.6 kgs), again a scan a week or so before had estimated him well over 9 pounds
So my advice would be try not to worry (of course easier said than done), the fundal height has grown (and at the expected rate if you are still only 2cm behind). Although if offered another scan I would probably go for one just for the reassurance.
Good luck :-)