Placenta previa refers to placenta praevia, there is no clear scientific statistics on the time of clean bleeding, it may be 3~5 days or 5~7 days or longer. Placenta praevia refers to the placenta completely covering or partially covering the endocervical opening after 28 weeks of pregnancy, pregnant women may experience painless vaginal bleeding, there is no clear scientific statistics on the time of vaginal bleeding, and it needs to be judged according to the severity of the condition as well as the treatment. Vaginal bleeding caused by placenta praevia in pregnant women, if the condition is relatively mild, timely hemostatic symptomatic treatment, bleeding may be cleaned up in 3~5 days. If the condition is severe and treatment is not effective, the bleeding may last for 5-7 days or longer. If a pregnant woman has vaginal bleeding caused by placenta praevia, she needs to go to the obstetrics and gynecology department of the local public hospital in time for diagnosis and treatment to avoid serious complications.