I read in the notes I got when my scan date came through that missed miscarriages happen to about 2% of people who go for their 12 week scan. I was one of those unfortunately. I had no reason to think that I'd miscarried though. I didn't really have any symptoms, apart from sore boobs, but then that's normal. Not everyone does have symptoms. The only thing was just that I didn't feel connected to the pregnancy. Sounds weird but I just didn't think it seemed real. I remember saying to my husband when we were in the waiting area "hopefully after the scan, it'll start to feel more real" but obviously it didn't because I'd miscarried.
This time round, I did feel different. But then that could be because we'd waited so long. But I had lots of symptoms and then we had an early scan at 8 weeks and all was fine.
It's natural to worry but it seems like it's not very common if it's only 2%! x