The main clinical manifestation of preterm labor is a small amount of vaginal bleeding or bloody discharge caused by uterine contractions, and abdominal pain may be present. Initially, the contractions are irregular and later develop into regular contractions. In this case, we should go to the hospital to take symptomatic fetal preservation treatment or terminate the pregnancy if necessary. 2. placenta praevia: the bleeding of placenta praevia is often unprovoked, painless and recurrent vaginal bleeding. As the uterus increases, the placenta attached to the lower part of the uterus and the cervical area cannot be stretched accordingly and causes misalignment and separation resulting in bleeding. If the bleeding is low and the fetal heartbeat is normal, you can use hemostatic drugs and continue to wait for delivery, but if the situation is more serious, the pregnancy should be terminated in time. 3. The reason for bleeding is early placental abruption, originally the placenta should be delivered after the birth of the fetus with the uterus, but early placental abruption is before the birth of the fetus was stripped. If you suspect placental abruption, you should immediately go to the hospital for corresponding examination and take corresponding treatment measures. 4. other: abnormal vaginal bleeding may also occur during pregnancy when cervicitis, celiac disease and other diseases occur, usually combined with the corresponding signs and fetal development may not be abnormal. In this case, a comprehensive examination is needed to identify the cause and provide timely treatment.