Brown discharge from the vagina of a pregnant woman usually indicates vaginal bleeding, which is often caused by preeclampsia, placenta praevia, uterine pathology, and so on. 1. After pregnancy due to abnormal embryonic development, physical weakness, overwork, trauma and other reasons, leading to the occurrence of preeclampsia, the uterus will have a small amount of bleeding, these blood with the discharge of vaginal secretion is manifested as brown discharge. 2. Pregnant women with placenta praevia are prone to painless vaginal bleeding in the middle and late stages of pregnancy. At the beginning of the bleeding, which is sometimes characterized by a small amount of bleeding, a brownish discharge from the vagina will be observed. 3. Inflammation of the cervix, polyps and other lesions can cause the cervical tissues to be more fragile and prone to rupture and bleeding. Pregnant women with brown vaginal discharge should go to the hospital in time for relevant examinations and treatments.