HELP!!! OB Says bub will be a "fair size" - do OBs get it right???

[AnnaBelle]

I saw my OB yesterday and during the visit he said to me (after feeling baby's position) "Oh I think this baby will be a fair size...it wont be a 6 to 7 pounder..probably an 8 something!!!"
Now how can he tell just by feeling the baby??? He didnt measure me or anything??

We had a chat and then we looked back at my 34 week scan (4d) which measured bub at 2383 grams or 5lbs & 4 oz...according to the scan bub is right on the 50th percentile for weight at 34 weeks. The scan report said that at 40 weeks estimated weight would be about 3500 grams if weight steadily went on in a linear fashion.
I know that this is an estimate.

Anyway my scans have always shown bub to be ahead of my LMP dates.
My scans estimate a due date of 20/11/08
My LMP estimates 26/11/08

So yesterday my OB was ??? looking at me as 38 weeks +1 day according to LMP
while my scan dates have me at 39 weeks exactly yesterday.

Furthermore I have not put on any weight in the last 5 weeks???

Its probably all academic and I am probably getting all excited for nothing but
this is my first bub!!

Just wondering really how much attention should I give to estimated size before bub is born and how accurate are these estimates?
I mean he didnt measure me or anything??

TIA
Anna

p.s. Thanks for your great advice and supportive answers on this subject - I just thought I would add that my 12 week scan & 20 week scan both said EDD
to be 20/11/08 so measuring 6 days ahead of EDD according LMP. I dont think I am all that big at all - just all baby and the fact that I have not put on any weight in the last 4 to 5 weeks must say something. Anyway 8 pounds is not all that big and with all your support I know I can do it!!!
I was 8 ld 9 oz myself & DH was just over 7 pounds if that counts for anything!!! I have not really dropped and not having any pre- labour pains in any major way so I dont feel that bub will come before the 26th anyway - so I guess as each weeks goes by I worry myself that bub is getting bigger and bigger - oh stop it i am driving myself nuts!!!!!!!!!!