I removed my mods and cc to see if that made her normal again but it didn't she looks like she's pregnant. It even looks like that in CAS
Edit By Crinrict: Adjusted Title
Please use th...
Ideas
Saves are not even needed with this one: just go on the gallery, and download families with children. Some of them will have this issue (tested with families in my gallery - Down-In-Simsland, or my brother - simsontherope).
So it's purely an hypothesis at this point, but seeing it affects all my children makes me wonder: I always create children in cas as teens, modify their features for them to look good when they will age up, then turn them into children (without saving the family or going in-game in between). Maybe that's why they retain some body features they are not supposed to show as children as body sliders should be unavailable / not displayed.
It happened to one of my sims kids as well and he never was a teen before. He was born in game and I haven't checked how he would look like as a teen or adult. So I don't think that's the only reason it happens :(