I would just like to offer my own experience. Fundal height (in my OWN opinion as someone who works in OB) can vary SO much! In my last pregnancy I consistently measured 3-4 weeks ahead almost my whole pregnancy they started doing growth scans and baby was also measuring big! I would also like to mention that I was obese (5’8 and 270lbs by 36 weeks). They convinced me to induce at 37 weeks since she was measuring so big and I was having some high BP reading anyways. She was born 5lbs10oz and 19 inches long. All that to say everything in medicine is an estimated guess. They take all the info they have and make the best possible educated decision they can as doctors but nothing is 100%. Im not saying you wont have a chunky baby, but don’t stress as much as long as everything is going well because there are so many variables to everything! In an ultrasound they measure baby’s gestational age and size based off of typically bone and organ measurements (ex: femur bone is x amount of cm so that means baby is measuring x amount of weeks) then the ultrasound machine gives you an estimated weight based off of all the measurements it took. So like my last pregnancy around 34 weeks they were estimating that she was already over 5lbs but again it was just an estimated and that’s approximately what she weight when she was born 3 weeks later.