Sudden bleeding in the third trimester of pregnancy, which is a symptom of miscarriage, if the bleeding is more is the need to go to the hospital in time, as soon as possible to stop the bleeding, at the same time applying birth control drugs for treatment, to avoid leading to the occurrence of miscarriage, go to the hospital for examination, be sure to look at the location of the placenta. Because the placenta has appeared in the third month of pregnancy, if the placenta position is relatively low, which is usually referred to as low placenta, during pregnancy will lead to repeated bleeding. If the bleeding is heavier and it is a central placenta previa, you must be prepared for abortion because it is not easy for the placenta and the fetus to develop to full term. If the vaginal bleeding is caused by miscarriage, it is sufficient to apply birth control medication under the supervision of the doctor, but at the same time, it is also necessary to see whether the bleeding is caused by cervical reasons.