Bleeding in mid-pregnancy may be caused by miscarriage, placental abruption, gynecological diseases and so on. 1. Pre-eclampsia: Although the fetus is more stable in mid-pregnancy than in early pregnancy, there is still the possibility of pre-eclampsia. For example, if you have intercourse in mid-pregnancy, too frequent or rough movements will cause bleeding, abdominal pain and other manifestations of pre-eclampsia. 2. Placental abruption: Placental abruption may occur in pregnant women due to high blood pressure in pregnancy or trauma, etc. After placental abruption, blood collects between the placenta and the uterine myometrium, which may cause bleeding and abdominal pain. 3. Gynecological diseases: pregnant women with gynecological inflammation, such as cervicitis, cervical polyps, or other cervical lesions and other gynecological diseases may also cause bleeding in the middle of pregnancy. In short, there are many causes of mid-pregnancy bleeding, you need to go to the hospital in time to do the relevant examination, for the cause of vaginal bleeding, the doctor for appropriate treatment.