Dark blood is usually a good indicator that it is old blood and needs to come out at some point.
I had the same thing and this being my first pregnancy, scared me to death! I called my ob/gyn the next morning and they said that its pretty normal to have some funky discharge from time to time because the cervix is so sensitive and engorged with tiny blood vessels but that it was typically nothing to worry about. They said not to worry unless it was bright red and quite a bit of it, so I felt much better, and hope that eases your mind some too. Good luck and God protect you and your little one!
Yes, Brown discharge is normal, its simply old blood!!....Dont worry at all unless you start getting fresh red blood!!..... =]