Bleeding at 39 weeks of pregnancy may be a physiological phenomenon, or it may be caused by placenta praevia, placental abruption, cervical polyps and other reasons. 1. Physiological phenomenon: when there is a small amount of vaginal bleeding accompanied by cervical secretions at 39 weeks of pregnancy, it is a normal physiological phenomenon, which means redness, and is a reliable sign before labor is initiated, and most of the time, labor will be initiated within 24-48 hours. 2. Placenta praevia: It can also cause vaginal bleeding without abdominal pain, without obvious triggers, and recurring, combined with medical history and ultrasound can help diagnosis, after a clear diagnosis, we should strengthen the management, and according to the amount of bleeding and ultrasound suggestive of placenta praevia, to terminate the pregnancy at the right time, in order to ensure the safety of mothers and babies. 3. Placental abruption: it will also manifest as vaginal bleeding, accompanied by abdominal pain, increased uterine tension and uterine pressure, slowing or disappearance of the fetal heart rate, and in severe cases, the abdomen is like a plate, combined with the clinical manifestations, ultrasound examination, etc. can be a clear diagnosis, and terminate the pregnancy as soon as possible. 4. Cervical polyps: they can also cause vaginal bleeding without pain, and can be clearly diagnosed by gynecological examination. Bleeding in 39 weeks of pregnancy need to go to the hospital as soon as possible, and as soon as possible to identify the cause, and actively deal with.