I got a s/m and it fit nicely. It's a little big in the chest, but I wore a bralette and it looked fine. So cute I love it! I have it 4 stars because the material is not very nice, but it's what you pay for.
It's very cute and well made- which was a relief, and looks just like the picture! However, I'm a 32DDD and my chest made it look really weird. My boobs kind of stretched it out on the sides, and the low-cut top was too revealing for me. Also it's hard to wear a bra with it. I'm (finally) starting to get a butt and it was on full display when I tried to bend over. It bummed me out because it was adorable, but I think you have to be relatively flat to pull it off.
As you can see, it's way too big in the top. I'm a B cup but you probably don't believe that 😂. The material is kinda cheap feeling but it's exactly what I was expecting. I guess you're supposed to have a shit ton of boob for this romper? Idk I might try to get it altered and probably put a white bralette underneath. Not mad, it's what was expected (sorry for the messy room)