The sudden appearance of vaginal bleeding symptoms in the third month of pregnancy is generally considered to be a miscarriage, the causes of miscarriage are more, including non-disease factors and disease factors, you need to immediately consult a doctor, for the condition of fetal preservation treatment or surgical treatment to clear the uterus, the causes and treatment are as follows: 1, miscarriage causes 1, non-disease factors: the embryo is still unstable in the third month of pregnancy, may be due to excessive fatigue, emotional fluctuations of pregnant women The miscarriage may be caused by factors such as trauma, collision or stimulation of sexual life, causing uterine contraction; 2, disease factors: it may be caused by malformation of embryonic development, embryonic genetic deficiency, luteal insufficiency of pregnancy, placental abruption, etc. The fetus is still alive and the cervical opening is not open, so it may be a pre-eclampsia miscarriage, so you should be hospitalized as soon as possible for fetus preservation treatment, and pay attention to bed rest; 2, the operation to clear the uterus: if the fetus is abnormal, the cervical opening is open and the bleeding is large, it is basically an incomplete miscarriage or inevitable miscarriage, so there is no hope to keep the fetus, so you should immediately perform emergency operation to clear the residue in the uterine cavity.