The risk of placenta praevia usually starts to increase significantly at 34 weeks of pregnancy and the level of risk is also related to the type of placenta praevia. The risk of placenta praevia increases significantly at 34 weeks of pregnancy and depends on the type of placenta praevia. In general, placenta praevia will start to cause painless vaginal bleeding at 32-34 weeks of pregnancy. Placenta praevia is a condition in which the placenta is lower than the nuchal translucency after 28 weeks of gestation and is attached to the lower part of the uterus, with its lower edge reaching or covering the inner opening of the cervix. According to the degree of covering the cervix, placenta previa can be categorized into complete placenta previa, partial placenta previa and marginal placenta previa. Clinical manifestations are painless recurrent vaginal bleeding without cause in the middle and late stages of pregnancy. Complete placenta praevia bleeds more, seriously endangering the fetus and the mother, and often can only be resolved by choosing cesarean section. Borderline placenta praevia bleeding occurs late in pregnancy and after labor, and is less frequent. Partial placenta previa tends to bleed repeatedly, leading to maternal anemia. The risk of placenta praevia hemorrhage increases after 28 weeks of pregnancy as the frequency of painless contractions increases, especially after 34 weeks of pregnancy when the risk of hemorrhage begins to increase significantly. For the placenta previa pregnant women can not cohabit, can not do strenuous exercise, can not cause obvious contractions, and even for obvious contractions should be given a certain amount of drugs to inhibit contractions, placenta previa is generally between 34-39 weeks of pregnancy should be terminated early to prevent hemorrhage. It is recommended that women in pregnancy should take obstetrical examination on time to detect abnormalities of the placenta in time, and should consult a doctor in time to take professional measures for treatment if there are any discomforts.