My newborn was 8lb (3638g) and dropped 340gms in the first three days - he is more than made up for it and is now 3890g (ie 8lb 9oz approx) two weeks postbirth and still fits 0000 comfortably (or 000 if bonds). In fact my first son was almost 9lb at birth (but lost over 10%) and he fit 0000 for a couple of weeks too. I would expect 00000 may be too small unless they lose a lot of weight in those first few days or the outfit is large for it's size.

In saying that however Kirsty is spot on their can be a great variation in size between what a doc thinks size wise and what you actually have. The ultrasound I had a week before DS was born indicated 8lb 6oz at that stage and a week later he came out at 8lb (born at 37.5wks). In saying that however none of my docs would predict a weight except to say that he was a good size and the best estimate they had was the ultrasound but to give or take a pound or two even on that.

FYI 2810g is approx 6lb 3oz
Sorry for waffling