Another thing to consider is the fact that many times, your baby will not grow as fast in the third tri. I was consistently told that Charlie was measuring 4 weeks ahead in size, but at 33 weeks things slowed down and he was born full term at 7lb14oz vaginally, and I'm not very tall either at 162cm. My Dr said that the believed that he may have a large head (and it was at 37cm) but that's about as much of a guess that he could hazard. Because unfortunately - and my Dr admitted this - it's a very inexact science and no one will quite know how big your baby will be until it's born.