is it always referred to as postpartum? check https://next.amboss.com/us/article/Ek08pT?q=endometritis#Zf8e1decd77cd3c6b37f3d2ffebf3dbba, not sure though
https://next.amboss.com/us/search?q=endometritis&v=overview dont think this is correct, it can have other reasons, see link