I bled with all 3 of mine. The dr. said some light bleeding is normal in the first trimester and is caused by the implantation of the egg in the uterus. I had something more than that with my first pregnancy.
It was a little different from my normal period but seemed heavy enough to be a period. I used that period as the date of my last period. It screwed up my whole due date! My son was born 3 weeks "early." When I look back, it was more like 2 weeks late:) Then with my other two, I bled off and on for several days with each for a couple of months. It was brownish in color so the doc didn't worry too much.
If you are ever concerned or nervous about it, contact your doctor. There is already so much stress during pregnancy; don't let bleeding add to it. And just keep an eye on any changes.