There are several ways to determine if a placenta praevia is present: first, it can be determined by checking the medical history and the symptoms manifested during pregnancy. If repeated painless vaginal bleeding occurs during pregnancy, placenta praevia is more likely because placenta praevia is characterized by the occurrence of painless vaginal bleeding. If the placenta is found to be covering the inner cervical opening or is close to the cervical opening during ultrasound, it is considered placenta praevia. Secondly, ultrasound examination can clearly show the relationship between the uterine wall, fetal previa and placenta cervicalis, and can clearly determine whether placenta praevia is present. If the placenta praevia is detected, you must pay attention to your body maintenance. After 28 weeks of pregnancy, preterm labor is likely to occur, so you must pay attention to it and avoid strenuous exercise and intercourse to avoid bleeding and infection.