Trying to lose weight while pregnant is not advisable. Also don't trust the scan when it's about baby's size. I gave birth on Feb. My baby was born premature. I had some complications while pregnant and one of them was gynae said my baby was big. My belly does look HUGE because my amniotic fluid was much higher than anyone else. But my baby was born at a perfect weight less than 3kg at 35w6d. So yes, don't worry about it. It's never accurate.
The weight is just estimated. Early week 3x my gynae also said my baby was big.. after that stabilized n increase slower.. estimated at 39 wks+2 was 2.85 but i gave birth at 39wks+5 or +6 was 2.585..
Mine was 2.1 at w 35.. to me doesnt feel big leh.. i have never heard that they measure the stomach! Dun worry.. mine was in breech position n gynae mentally prepared me that i may need c sec.. end up also no nd..
yakyakyeh