A friend of mine had an estimate done at 38 weeks and was told her baby was 9pounds, she ended up going in for a C Section the day after her due date and her baby ended up being 8.5 pounds. So I wouldn't worry to much, I have been told they are not always correct. My Cousin didn't even get a scan or estimate on her baby and they just told her he feels like he would is average size around 7-8pounds and she ended up trying to get him out for 18hrs and then had to have an emergency C Section and when they weighed him he was 10pound 10ounces! Her first baby as well and she is only small, but she was 2weeks overdue!