I'm not asking this to be rude...I'm genuinely curious

Ms
So you know how when you get farther along the doctor measures your belly to see if you are growing right.
Well how does that work for larger ladies?
Wouldn't a fluffy stomach throw off the size?
I have always been tiny, and I'm all belly now that I'm pregnant. But how does it work for larger ladies?
I hope I didn't offend anybody, I'm just genuinely curious.