Vivid dreams are one of the many symptoms related to being pregnant, I'm sure it's not a premonition, it's probably just your insecurities working their way out through your subconcious.

We were talking about this the other day, read this thread to see some of the weird dreams the rest of us are having:
Stupid dreams

i know exactly what you mean. Last night I had a cople of sharp pains, then had an extremely vivid dream that I had a m/c. This morning when I woke up and went to the loo there was blood!!! I just spent 6 hours in A&E - they couldnt explain the bleeding but everything is fine - they did an u/s and we saw the little one with a nice healthy heart beat. So it was just what it was - a dream. Good luck with your scan!