It can depend HUGELY on which way the baby is laying! At my 36 week check they checked my height, I was always 2cm more than my weeks from about 20 weeks, and I was 42! She said "oh that can't be right" and checked it again, same thing. The MW goes "um I am going to get the doc" which scared the bejeebers out of me. I got up and walked around when the doc came he checked me and I was only 39! She checked as soon as he walked out and I WAS 39, Ash must have been laying funny she said.