Complete placenta previa occurs when the placenta completely covers the mouth of the uterus. The only way to safely deliver the fetus is through a C-section because placenta must be detached and expelled in order for the fetus to enter the birth canal. Placental abruption is premature detachment of the placenta from the uterus, which does not always require a C-section. Marginal placenta previa occurs when the edge of the placenta is against, but not covering, the mouth of the uterus. This will often, but not always, require a C-section. Placenta accreta occurs when the placenta invades the wall of the uterus. Technically, the baby can be delivered vaginally, but this condition often requires a hysterectomy to prevent maternal death due to hemorrhage. When diagnosed antenatally, a cesarean section is the delivery of choice.