The most common cause of brown pregnancy bleeding is pre-eclampsia, which is manifested mainly by vaginal bleeding and abdominal pain. When the amount of vaginal bleeding is not a lot, the vaginal bleeding accumulates in the vagina and is discharged out of the body after a period of time, it is manifested as bright red blood turning brown, so the bleeding is brown blood. At this time, you can not panic first, you can rest at home in bed and observe. If the vaginal bleeding slowly decreases after bed rest, you can observe it first. If the amount of vaginal bleeding becomes more and more, even more than the amount of menstruation, or if it is accompanied by pain in the lower abdomen, you need to consult a doctor as soon as possible to find out the more exact cause and carry out symptomatic treatment.