Hi, The cm's refers to your fundal height. My maternity book (which I have to take to each visit) has a chart in it. It says that at 30 weeks 26cm is on the lower end of the scale 29 is average and 32cm is on the larger end so it doesn't seem too far off. Have a look in your maternity book. I went for my 16 week check up and I was measuring 16 cm which was on the large end of the scale. for 16 weeks it varied from 9-16, but my last baby was 9 lb 15, so I am expecting one about the same this time. Good luck and don't worry, there's nothing you can do so just enjoy your bump.