Brown discharge in the third month of pregnancy may be caused by low placental position, uterine contraction, pre-eclampsia, ectopic pregnancy, etc. It may also be caused by other diseases, such as vaginitis, cervicitis, etc. It is recommended that pregnant women go to the hospital for ultrasound examination in time to clarify the cause and treat the cause. 1. Low placental position: As the third month of pregnancy belongs to early pregnancy, the uterine cavity is relatively small at this time, and the placenta has just formed, often The placenta is just formed and often attached to the lower part of the uterus, or the lower edge of the placenta reaches or covers the inner cervical opening, which may cause a small amount of vaginal bleeding and then brown discharge. In this case, you should go to the hospital in time, and pregnant women should pay attention to bed rest and avoid straining. 2. Uterine contraction: due to overworking pregnant women, sexual life, etc., stimulation causes uterine contraction, and then brown discharge may appear. Pregnant women should rest in bed, go to the hospital for ultrasound examination in time to observe the specific situation of the fetus and the pregnant woman, and use drugs to inhibit uterine contraction for treatment under the guidance of the doctor; 3. The symptoms may include vaginal bleeding in small amounts, followed by brown discharge. Pregnant women should take proper rest, reduce activity, supplement nutrients, use progesterone therapy under the guidance of a doctor, actively control underlying diseases and perform fetal preservation therapy. If the vaginal bleeding stops and ultrasound examination indicates that the embryo is alive, the pregnancy can be continued. If the clinical symptoms are aggravated and irreversible, it indicates that miscarriage is inevitable and timely termination of pregnancy is needed; 4. ectopic pregnancy: tubal-related lesions are more common, with typical symptoms of abdominal pain, irregular vaginal bleeding, dark red color and small amount, and then brown discharge may appear, which can be treated by applying medication or surgery as prescribed by the doctor; 5. other diseases: if it is caused by vaginitis, cervicitis and other gynecological inflammation If the brown discharge is caused by vaginitis, cervicitis and other gynecological inflammations, generally pay attention to observation and regular checkups. If brown discharge persists, promptly seek medical treatment accordingly.