Its old menstrual blood mixed with vaginal secretions. If it keeps up for more than a few days and doesn't change colors or consistency you should call a doctor. If it has a foul odor go to the doctor!
I'm pregnant and I have been having brown discharge. I could becoming from your imbalanced hormones. When pregnant, your body goes through so many changes. But to be on a much safer side for you and the baby, check with your doctor. The sooner the better.Why am I having thick brown discharge?