Brown discharge at 18 weeks of pregnancy may be a case of bleeding from low lying placenta or preeclampsia. Placenta hypoplastic state bleeding is the placenta attached to the lower end of the uterus, or even the lower edge of the placenta reaches or covers the inner mouth of the cervix, its position is lower than the prenatal part of the fetus, once there is a contraction, external force, exertion, strenuous exercise, coitus, and other stimuli will make the blood sinus open and cause bleeding. Pregnant women with preeclampsia have a small amount of bleeding from the uterine cavity, and the blood oxidizes and turns brown after being retained in the vagina and is discharged with secretions, which can sometimes be combined with abdominal pain. Brown discharge at 18 weeks of pregnancy, you should go to the hospital in a timely manner, ultrasound examination, to clarify the location of the placenta and the bleeding in the uterine cavity, according to the results of the examination to decide on the treatment plan; in addition, it is recommended to pay attention to the rest of the pregnancy, regular obstetric examination, if ultrasound suggests that the placenta is low lying state recommended more rest, less activity, to avoid bleeding.