My little one has been measuring small since my 24week anatomy scan. She was in the 9th percentile for head size but the rest of her measured perfect with my due date, which is Today Nov 24th, no baby still though. They made me do another anatomy scan at 28weeks and she was in the 7th percentile. By that appointment I gained 10lbs lol because I was trying to eat alot to make her grow. It didn't work. My Doc said there really isn't anything they can do, she will just be on the smaller side more than likely.
babies all go through growth spurts at different times. my baby was measuring large and further along at 20 weeks, my Doctor said it is all genetics as this point. I would stay calm and as long as there is progress in 2 weeks there is nothing to worry about :)
I'm 29 weeks and my doctor haven't measured me yet.