I bought a reasonably priced wool swing coat that came to about my knees. It came with a belt. As I got bigger, I removed the belt. I left it open if I got too hot and it still looked nice.
Added a scarf and felt dressy enough for work. Also worked with jeans, etc.
I wore it again afterwards because I cinched it in with a belt.
Pretty sure I've seen swing coats recently. The other thing I've seen is women wearing those poncho style wool coats, or those wool wrap coats (with no buttons, just the big belt).
I just got it a tiny bit bigger than normal (but not maternity) and then I was able to wear cardigans and blazers afterwards with it.
Good luck :)