Brown discharge in pregnant women can be caused by implantation, pre-miscarriage, ectopic pregnancy, cervical polyps, preterm labor and other reasons. 1. The period of implantation: when the fertilized egg is implanted, some women will have a small amount of brown vaginal discharge, accompanied by a slight pain in the lower abdomen, usually in 3 to 4 days after the disappearance of their own, is a normal physiological phenomenon. 2. Pre-eclampsia: the symptom of brown vaginal discharge, accompanied by paroxysmal pain in the lower abdomen, can be combined with the history and ultrasonography, serum progesterone test, etc. to make a clear diagnosis. 3. Ectopic pregnancy: it can be manifested as a small amount of brown vaginal discharge, accompanied by one side of the lower abdomen pain, can be combined with medical history and signs, ultrasound, blood hCG test to assist in the diagnosis. 4. Cervical polyps: can cause repeated vaginal bleeding brown discharge, not accompanied by abdominal pain, can be diagnosed through gynecological examination. 5. Prolonged labor: in late pregnancy, before labor starts, it can also be manifested as a small amount of brown vaginal discharge, accompanied by irregular pain in the lower abdomen, usually within 24 to 48 hours of labor. Combined with the clinical manifestations can be clear. When pregnant women have brown discharge need to go to the hospital, and identify the cause, under the guidance of the doctor to deal with.