Strengths and limitations
Among the similar retrospective studies, to our knowledge, this study is the largest cohort with 747 women who gives subsequent cesarean birth with placenta previa after the first cesarean delivery, since this kind of medical situation is rare in clinic, but, with life-threatening consequences. These patients were from 13 hospitals located in the different regions of China. Although these hospitals belong to the first-class hospitals in China and represent the top level of local medical care, the regional differences on medical care are existed among these hospitals, which may cause the variation of the outcome occurrence and treatment, and can be considered as flaw for the present study. However, the obtained conclusions are still national representative. Another key finding in our study is that the examination of ultrasound combined with MRI largely improves the prediction of potential outcome in the patients, which can used to follow up patients in order to prevent and treat the potential severe complications. Finally, we also demonstrate that vascular occlusion does not affect massive bleeding in patients, which is disagree with the current opinion. But, we have to point out that vascular occlusion in the current study is performed only in 106 patients, among whom the different strategies for vascular blocking is applied, which is another limitation for this study and more cases and prospective study are needed to confirm our conclusion.