If you are 13 weeks pregnant and you see red that means there is vaginal bleeding. There are many reasons for vaginal bleeding at this time, such as preeclampsia, cessation of embryonic development, placenta previa, placenta praevia, cervical polyps, cervicitis, precancerous lesions of the cervix, cervical cancer, all of these reasons may cause vaginal bleeding, so it is necessary to go to the hospital for ultrasound and gynecological examination in a timely manner. If the bleeding is caused by pre-eclampsia, it needs to be treated with fertility preservation; if it is caused by placenta praevia or placenta praevia, it is necessary to pay attention to rest, not to do strenuous activities, and appropriate application of drugs to preserve the fetus; if it is caused by cervicitis, pre-cancerous lesions of the cervix, or cervical polyps, it is necessary to carry out localized treatments.