6weeks2days

I went into the er bc I had some spotting this is my third pregnancy and usually do to me being o negative I was spotting darkbrown/dark red

They did a transvaginal ultrasound and there was no heartbeat, they said I will be have miscarriage, we’re devastated my question is how long will it take to miscarriage and have this Pass ?? Is it possible I’m to early I go to the dr tomorrow for another ultrasound and I’m terrified. I’m still having dark brown spotting with no cramping .