I have always been more to the overweight side so my doctor has always been good with no weight gain or losing some weight. As long as baby is growing, your getting the nutrition you need, and your measuring good then there is no need for weight gain. My last pregnancy i was 15 lbs lighter right after having the baby. All my clothes were too big haha.
My doctor at first said my whole pregnancy I should gain no more than 25 lbs. I'm around 190 and he said I should either not gain at this point or I can lose weight cuz of my size. So far I haven't gained but I'm only 19 weeks and he's happy I haven't gained. With my first I gained all at the end so most likely the same for this one.