Are vivid dreams/nightmares really a symptom of pregnancy?

So I am 9 DPO. Last night I had some crazy dreams. One was so vivid and horrific that I had to wake myself up in the middle of it. It has stuck with me every since. I cant remember the last time I had a dream like that. So I was telling my best friend about it this morning and she said she started having really detailed and funky dreams around the same time as me and then soon after found out she was pregnant. So I am curious are dreams really a symptom? Or is this conicidence?