Brown discharge in 3 weeks of pregnancy may be due to the fertilization of the egg, premature miscarriage, cervical erosion and other reasons, need to be specifically analyzed. 1. Fertilized egg implantation: In early pregnancy, when the fertilized egg is implanted in the uterine lining, it may cause a small amount of vaginal bleeding, resulting in the occurrence of 3 weeks pregnant with brown discharge, the symptoms will gradually disappear after 2~3 days. 2. Pre-eclampsia: If a pregnant woman experiences pre-eclampsia, it may lead to abnormal shedding of the uterine lining, which usually results in brown discharge, accompanied by symptoms of abdominal pain. 3. Inflammation of the cervix: after pregnancy, due to the increasing levels of estrogen and progesterone in the pregnant woman’s body, the columnar epithelium of the cervix moves outward, tissue hyperplasia, and the symptoms of cervical erosion significantly worsened, and at this time, if there is infectious inflammation, it is easy to vaginal bleeding, which will lead to 3 weeks of pregnancy with brown discharge. If a pregnant woman is experiencing brown discharge in the third week of pregnancy, accompanied by the above symptoms, it is recommended that she consult a doctor in a timely manner, under the guidance of the doctor, improve the relevant examination, clarify the cause of the disease, and symptomatic treatment.