Based on the description of the product, I purchased a 4x instead of my normal 2x. I'm glad that I did! The fit is fine. No issues there. But I'm 5'9" and the length of the garment leaves a little to be desired. If I'm standing straight up or laying flat in the bed, the fit is fine. If I move a leg? Wedgie City. So if you are tall or have a longer torso, this may not be for you. I'm considering cutting the bottom half and turning it into a nightgown instead of a romper.
Buy a larger size or else!