I found this information which I really interesting, it shows the average weight for gestation, I found the same chart or very similar versions in a few different locations, no wonder they were asking if she was a couple of weeks further along as N's weight was between the average for a 34/35 weeker as was her length

Gestational age... Length (cm)........ Mass (g)

22 weeks........... 27.8cm ...........430grams
23 weeks........... 28.9cm ...........501grams
24 weeks........... 30cm ...........600grams
25 weeks........... 34.6cm ...........660grams
26 weeks........... 35.6cm ...........760grams
27 weeks........... 36.6cm ...........875grams
28 weeks........... 37.6cm ...........1005grams
29 weeks........... 38.6cm ...........1153grams
30 weeks........... 39.9cm ...........1319grams
31 weeks........... 41.1cm ...........1502grams
32 weeks........... 42.4cm ...........1702grams
33 weeks........... 43.7cm ...........1918grams
34 weeks........... 45cm ...........2146grams
35 weeks........... 46.2cm ...........2383grams
36 weeks........... 47.4cm ...........2622grams
37 weeks........... 48.6cm ...........2859grams
38 weeks........... 49.8cm ...........3083grams
39 weeks........... 50.7cm ...........3288grams
40 weeks........... 51.2cm ...........3462grams
41 weeks........... 51.7cm ...........3597grams
42 weeks........... 51.5cm ...........3685grams
43 weeks........... 51.3cm ...........3717grams