This is not necessarily the case, because placenta praevia can occur for a variety of reasons, some of which are excessive downward migration of the fertilized egg, and another is that the placenta is relatively large. The placenta is larger, so it is easy to develop placenta praevia. The other is that there are more miscarriages or abortions before pregnancy, resulting in damage to the endometrium, which may increase the chance of placenta praevia occurring again, but not necessarily placenta praevia. When the first operation was done for placenta praevia, in this pregnancy, it is usually recommended to have an ultrasound early on to rule out the chance of a scar pregnancy of the fertilized egg, which is still a greater risk. The general rule is that the first time is placenta praevia and the second time an ultrasound should be done earlier to rule out the possibility of a scar pregnancy. If a scar pregnancy is found, it is usually timely to terminate the pregnancy, because scar pregnancy can lead to a high incidence of placenta implantation. If the placenta is implanted, this is the highest risk level in terms of obstetrics, with a high incidence of postpartum hemorrhage and hysterectomy.