I was BMI of 40, but lost weight slowly (and healthily) over 2010 to go down to BMI of 29 (less yummy cornbread/grits (transplanted American)) and was told by IVF clinic that I really needed to lose another 10lbs or so, but got pregnant naturally the month we were supposed to start hormone treatments/first cycle. Interestingly, I had regular, altho erratic cycles so we given metformin for PCOS and later, discovered had an underactive thyroid and with both medication, may have pushed my at that point, pretty healthy body into conception/sticky baby....
When we fell pregnant in June/July of this year, my ob/gyn refused to weigh me as she didn't want me obsessed about food/diet, etc., and was advised to just continue to eat healthily (so far, so good!), and my GP refuses to weigh me as well, as she believes that it would worry me too much.
I have had (so far) no serious problems in this pregnancy and altho I have no doubt gained weight, it is all baby and boobs....I had an mc and two possible chemicals before this pregnancy, so it is probably down to weight loss, healthy eating and gentle exercise that I am healthier today than I was ten years ago (and I was 43 when I conceived/will be 44 when I deliver -- so hope for everyone!)
best wishes
ps. baby doesn't like sweet things too much, so very helpful little one already!