I say that this fits somewhat small because I am 5'9" and I ordered and XL just in case which says it is for people from 5'9 to like 6'2 I believe. it was slightly short for me in the front but it still fit well enough as it's really stretchy. I am 5'9, 185 pounds, and a 36DD. If you plan on having any extra room in this onesie or wearing a diaper underneath it, go at lest one size up, two sizes if you plan on drying them in the dryer rather than hang drying them as I heard they shrink quite a bit. Otherwise, this is a wonderful product! when I took it out of the bag it seemed a bit stiff and not soft, but once I put it on it somehow was magically way softer. As I said before it stretches pretty well but if you have anything above a C cup I would recommend a size up for it to fit right. Overall I think it's cute and my daddy loves it