Hi,
Vivid dreams are very likely during pregnancy. Im not sure if anyone knows why but it is common to experience very strong dreams and nightmares.
I went through my pregnancy with about 200 other women on a messageboard. Many of us would often post about our strange dreams, some of them were even quite rude lol
I wish you all the best for your first scan, its amazing to see the baby there on a screen. Take plenty of tissues and some change for photos, it really is something special.
Oh and can i recommend the pregancy boards on ivillage.
http://www.ivillage.co.uk/pregnancyandbaby/boa rds/0,,,00.html they are great to join and you can make friends with many women in exactly the same position as you.