First of all congratulations!!!
Sorry if I’ve not understood your post / question properly -
I was a size 10/12 with my first pregnancy. However with my second (I am currently 37 weeks), I was a very different size! I was a size 16 and I had a high BMI (31.5) at my booking appointment. I have only been weighed once since that initial weigh in. So twice in total throughout this pregnancy.
The only difference I have found is that if your BMI is above 30 at your booking appointment, you are automatically put forward for a glucose / gestational diabetes test but you have a right to decline this. And then I think if it is above 40, you aren’t allowed a water birth (but please don’t quote me on that). I think it’s because it is harder for midwives to lift you from the pool if you are this size and there are complications etc.
I’ve not really restricted my food intake this pregnancy and when I was weighed for the second time (I think I was around 34/35 weeks), my BMI had only gone up to 32.5 or 33. So I think you’d have to eat an awful lot to go from just over 30 BMI to over 40.
I know it’s different with every trust but my weight hasn’t been mentioned at any appointments (even at my consultant appointments, let alone my midwife appointments) / hasn’t been an issue whatsoever

. I’m hoping for a VBAC and despite my size, the hospital have been so supportive and haven’t said the word “no” to anything at all. But if they do for you, remember everything is your choice, the NHS only has guidelines. Very very obese women go on to have natural births, average sized babies, no gestational diabetes etc! X