Interpretation
Previous cesarean history and current pregnancy with placenta previa can lead to placenta growth on the scar tissue of cesarean surgery, which is often accompanied with placenta implantation, resulting in unpredictable and uncontrollable severe outcomes (24). Unfortunately, it is quite difficult to precisely diagnose placental growth on the scar tissue of the uterus and placenta implantation. Meanwhile, this kind of pregnancies, in particular, with pernicious placenta previa in the subsequent pregnancy as in our study, are clinically rare and always had severe outcomes including massive bleeding, hysterectomy and even maternal and fetal mortality. However, up to now no national or international guideline has been published for the diagnosis and treatment of this critical situation in pregnant women, although a few reports have been published with very limited case numbers (25,26).
Among the 747 pregnancies in this study, 55.8% and 47.5% of them had massive bleeding and placenta implantation, respectively. Uterine rupture occurred in 0.8% of those pregnancies and 10.4% required hysterectomy. On the contrary, hysterectomy (22.4%) was reported as the most common severe complication in the pregnancies with placenta previa and prior cesarean delivery (27). The present study also found that MRI examination has higher sensitivity and specificity in determining placenta implantation than ultrasound. In line with our observation, MRI has been proposed for placenta implantation diagnosis due to its characteristics of wide field of vision, high resolution and contrast for the soft tissue (28,29). Importantly, placenta implantation predicted by both ultrasound and MRI, was confirmed later by the surgery. These pregnancies (56 cases) with ‘double-prediction’ of placenta implantation, also had a higher amount of bleeding during surgery and hysterectomy potential than women with MRI- or ultrasound-predicted placenta implantation alone. Therefore, MRI combined with ultrasound examination enabled not only to better determination of placenta implantation, but also the prediction of the outcomes of pregnancy.
The application of vascular intervention in obstetrics significantly decreased hysterectomy rate, blood loss and transfusion, and admission to intensive care unit (30–36) , particularly, in the pregnancies with placenta previa and prior cesarean delivery (37,38). Surprisingly, our results showed that the estimated blood loss during delivery had no difference between blocking and non-blocking group, and that the blocking group even had a higher hysterectomy rate than the non-blocking group. To support our observation, abdominal aortic balloon was reported to block artery circulation and reduce bleeding temporarily, and re-bleeding occurred once balloon was removed (39). Another study also showed that abdominal aortic balloon could not effectively reduce the blood loss in the patients with placenta implantation compared to the non-blocking group (40). The potential reason for this opposite conclusion between ours and others is that all other studies have a small number of patients, while 747 pregnancies from 13 first-class hospitals located in the different regions of China were included in this study. Combined these evidences, the published data and related complications (29,41,42) , we conclude that the effect of vascular blocking approach in blocking massive bleeding during the delivery indeed needs to be deliberated.