INTRODUCTION
Placenta previa often occurs in pregnant women who have had increased
age, multiple gestations, high parity, and smoke or use illegal drugs
(1). Cesarean delivery induced scar formation in uterine and
endometrial injuries also facilitates the development of placenta
previa in the subsequent pregnancies of women (2,3). It is estimated
that placenta previa occurs in 0.28-0.55% of pregnant women in the USA
(4). The overall incidence of placenta previa in China has recently been
reported to represent 1.24% of deliveries (5). Placenta previa can
cause severe maternal and neonatal complications including the
limitation of fetal growth, preterm birth, hemorrhage whatever the
degree of overlying placenta and gestation stage, hysterectomy and even
the mortality of the fetus and mother (6,7).
To avoid these consequences, cesarean section has been widely applied in
pregnancies with placenta previa. However, despite its important role in
managing dystocia, pregnancy complications, and reducing maternal and
child mortality and morbidity, cesarean delivery rates have increased
around the world (8,9). For example, in China, it increased from about
5% in the 1960s to 20% in the late 1980s and early 1990s (10). In
particular, cesarean sections made of 40-60% of deliveries in most
hospitals in China during the last 20 years (11,12). On the other hand,
cesarean history increases the risk of placenta previa by 60% in the
subsequent pregnancy of women (13). A pregnant woman who has both a
complete placenta previa and cesarean history is more likely to have
high risk of placenta implantation, severe bleeding during gestation and
delivery, and massive postpartum hemorrhage (14,15). More seriously, in
the case where the placenta grows on the scar of a previous cesarean
section, referred to as pernicious placenta previa, increases the risk
of placenta implantation by up to 50% (16). Both pernicious placenta
previa and placenta implantation are very critical and urgent situations
in obstetrics, in which fatal bleeding occurs very often during
delivery, and the maternal mortality rate is as high as 7% (17).
However, no collective data have been reported up to now to demonstrate
the severe outcomes and associated risk factors in patients with
pernicious placenta previa. To prevent severe bleeding during delivery
and severe postpartum hemorrhage in these patients, vascular occlusion
has been widely used in clinical practice, with methods such as
bilateral uterine artery embolization (UAE), internal iliac artery
embolization (IIAE) and intra-aortic balloon occlusion (18,19), although
their anti-bleeding effect and influence on the prognosis of pregnancies
remain unclear.
We performed a retrospective study in which data on 747 patients who had
pernicious placenta previa in their pregnancy following their first
cesarean delivery, were collected from 13 first-class hospitals located
in different regions of China. The severe consequences and associated
risk factors of these patients were analyzed. In particular, we
evaluated the approaches taken to predict severe outcomes and the
influence of vascular occlusion in preventing severe postpartum
hemorrhage and hysterectomy.