I had a blood clot in uterus but outside the baby sac too. It was detected during my 12th week scan. I didn’t experience bleeding either. Doc prescribed progesterone vaginal insertions to stabilise pregnancy and I did so for a month, then I noticed super dark brown to black discharge (not a lot) after. Went back for a scan and baby is healthy. I guess it is fine unless doc says otherwise! My doc didn’t mention too much of it too.