Both scarred uterus and placenta praevia are very dangerous comorbidities for the mother. 1. scarred uterus: when and for what did you have the uterine part surgery? If it was a cesarean operation, what was the reason for the cesarean delivery? It is better to conceive after 2 years of cesarean section and observe the thickness of the incision in late pregnancy. 2, placenta praevia is divided into partial placenta praevia (which includes marginal placenta praevia, this type has relatively low risk) and central placenta praevia, central placenta praevia is the placenta covering the whole inner cervical opening, the cervix gradually matures and shortens in late pregnancy, in this process the attached placenta will gradually separate from the cervix, painless bleeding occurs, the bleeding can be very large, this is the most dangerous. If the scarred uterus is combined with placenta praevia, the pregnancy should be terminated promptly at 37 weeks full term to reduce the risk.