How accurate is Dr.s guesses

Natalie

So, I've been feeling a lot smaller with baby number 2 and was worried he was going to be too small. Dr. Says he measuring fine, but is guessing he'll be 7 lbs ish at birth (as opposed to my 8.5 baby #1) how accurate are these guesses? I dont want to get all excited for a slightly smaller baby and then be taken off guard with a 9lb little one haha