A friend of mine who is currently 39weeks is measuring 5 weeks behind - she has been having weekly US for the last month or so however that was something else unrelated to the size - her baby is measuring perfectly on the scans - not huge but not tiny either I think she mentioned to me the other day that baby was already close to 8lbs and with 5cm behind in her fundal height you'd have expected alot smaller - she is pretty small herself too