Hi - I really would try not to worry. I measured small about 4 weeks behind from around 28 weeks onwards. Everyone commented on how small i was etc and this used to really upset me. I had a growth scan towards the end giving me an estimated birth weight of around 5lbs. Fin was born, granted 2 weeks late but at a very healthy 7lb 6. These thigns are really hard to predict, especially with the fundal measurements.
My sister in law had a 9lb baby first time around and then on her second was absolutely huge and measured a good 3 weeks ahead all the way through. Went 2 weeks over and shocked everyone with a 6lb 2 bubba.
Finley Sean 04/08/2009 7lb 6oz