Beware of Vaginal Bleeding Vaginal bleeding at any time during pregnancy may be a red flag. Vaginal bleeding in early pregnancy may be a sign of ectopic pregnancy or threatened miscarriage, although some women later become pregnant successfully. If vaginal bleeding is accompanied by abdominal pain, you should go to the hospital for examination. Vaginal bleeding after 20 weeks may be a sign of placenta previa or placenta detaching from the uterus. Both conditions are life-threatening to the mother and fetus, and you should go to the hospital immediately. During pregnancy, the surface cells of the cervix often change and cause bleeding, especially during sex.