In cases of placenta previa, there is also a certain risk of preterm birth. Generally, in the late stages of pregnancy, a persistent low-lying placenta may have some impact on the development of the placenta and embryo. Excessive physical activity or normal daily activities may cause abnormal vaginal bleeding. Long-term blood clots pressing on the cervix can also promote cervical dilation and lead to preterm birth. Therefore, it is generally necessary to rest in bed and avoid excessive exercise after placenta previa occurs, in order to reduce the risk of bleeding.