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.