Study population
The retrospective, observational study was approved by the Ethics Review Committee of West China Second University Hospital of Sichuan University, and because of the nature of the retrospective, observational setting for our study, and the data are anonymous, an informed consent was waived for all included patients by the Ethics Review Committee of West China Second University Hospital. All study methods of the retrospective study were conducted following the relevant regulations of a protocol approved by the Institutional Review Board from the West China Second University Hospital of Sichuan University. This study was conducted from January 2014 to December 2017. Placenta previa occurred when the placenta was wholly or partially implanted in the lower uterine segment. Placenta accreta was defined as the situation where the placental trophoblast invaded into the myometrium, according to the depth of villous tissue invasiveness. Placenta accreta has been subdivided by modern pathologists into “creta” or “adherenta”. An adherent placenta is where the villi adhere superficially to the myometrium without interposing the decidua. Placenta increta is where the villi penetrate deeply into the uterine myometrium down to the serosa. Placenta percreta is where the villous tissue perforates through the entire uterine wall and may invade the surrounding pelvic organs, such as the bladder [7,8]. All included patients had at least one prior CS and were diagnosed with placenta previa or placenta accreta when the placenta covered a previous cesarean scar by color Doppler ultrasonography and pelvic magnetic resonance imaging (MRI) examinations before delivery. The diagnosis was confirmed by intraoperative findings or histopathological examination after surgery. Patients with an adherent placenta were excluded in this study because balloon occlusion was not routinely used for these patients in our clinical work. Therefore, we only included patients with placenta increta or percreta. Patients with serious medical and surgical diseases, incomplete data, multiple pregnancies, or those who delivered before 28 weeks of gestation were excluded.
According to the above-mentioned inclusion and exclusion criteria, of 713 patients with placenta previa and accreta associated with previous CS who delivered in our hospital, 420 were included in this study (Figure 1). The 420 patients were divided into two groups according to whether they had PBOIIA (n=248, 59.0%) (balloon group) and whether they did not have PBOIIA (n=172, 41.0%) (control group). In 2017, doctors in our hospital investigated a novel approach called parallel transverse uterine incision (PTUI) surgery. PTUI had a significant effect on reducing intraoperative blood loss and the hysterectomy rate for patients with placenta previa and accreta [9,10]. Among our included patients, we found that some patients underwent PTUI surgery simultaneously. To avoid the effect of PTUI surgery on the results, we conducted a subgroup analysis on the two groups of patients according to whether they had PTUI surgery during CS. Among the 420 patients, 86 had PTUI surgery and 334 did not have PTUI surgery. In the PTUI group, the 86 women were subdivided into the balloon group that had PBOIIA (group A1; n=58) and the control group that did not have PBOIIA (group B1; n=28). In the non-PTUI group, the 334 women were subdivided into the balloon group (group A2; n=190) and the control group (group B2; n=144).
Comprehensive management of patients with placenta previa and accreta required the cooperation of a multidisciplinary medical team. All patients underwent scheduled CS at 35–36+6 weeks of gestation [11]. Fluid transfusion, blood transfusion, strong uterine contraction drugs, and conservative surgical treatments were provided to patients during CS. If the conservative treatments were not effective, hysterectomy was performed to save the patient’s life. Since the effectiveness of PBOIIA in patients with placenta previa and accreta remains controversial and it is not definitively reliable, and there are complications associated with PBOIIA. The decision of preoperative prophylactic placement of balloon occlusion was made on a case by case basis through preoperative multi-department discussion before surgery. This decision was jointly made by the surgeon and radiologist after evaluating the condition of patients in our hospital. All patients who accepted PBOIIA provided written informed consent, and balloon occlusion of the right and left internal iliac arteries was inflated in all cases.
Placement of the occlusion balloon
In the balloon group, all included pregnant women were fully informed of the benefits and complications of PBOIIA by their doctors before CS. For the surgical procedure, after routine disinfection and laying of towels, bilateral femoral arteries were punctured by the Seldinger technique and a 5-French vascular sheath was inserted. A 5-French Cobra and 0.035-inch guidewire were used to guide the balloon catheter into the bilateral internal iliac artery through the vascular sheath, with the balloon catheter tip slightly above the opening of the bilateral uterine artery (low-profile PTA balloon dilatation catheter PTA5-35-80-8-6.0; Cook Medical Inc., Bloomington, IN, USA). An indwelling catheter was fixed in both lower limbs and the patients were brought into the operating room. During the operation, approximately 2 mL of eunepiac, which is a diluent contrast agent, was injected to temporarily inflate the internal iliac artery balloon after the fetus was delivered and the umbilical cord was cut. This diluent contrast agent can block blood flow of bilateral internal iliac arteries and reduce the amount of uterine bleeding [12] (Figure 2).
Clinical characteristics and outcomes
The clinical characteristics of the included patients were collected by reviewing the medical records. The clinical indicators were retrospectively collected by two obstetricians, and if any discrepancy existed, it was resolved by a third obstetrician. All reviewers were blinded to the data of patients. The clinical indicators included maternal and neonatal characteristics, perioperative blood indicators, and surgical outcomes during hospitalization. Maternal and neonatal characteristics included maternal age, gravidity, parity, number of previous CSs and abortions, gestational age at delivery, body mass index (BMI), birth weight of the newborn, 1-min Apgar score, neonatal intensive care unit (ICU) admission, neonatal asphyxia, and neonatal death. Perioperative blood indicators included hemoglobin (HGB), hematocrit, platelets, prothrombin time, activated partial thromboplastin time, and fibrinogen. Surgical outcomes included intraoperative EBL, cesarean hysterectomy, packed red blood cell (PRBC) transfusion (in China, one unit of PRBC is approximately equal to 200 mL of whole blood), fresh frozen plasma transfusion, platelet transfusion, the volume of autologous blood transfusion, blood loss within 24 hours postoperatively, maternal ICU admission rate, postoperative pyrexia (≥38.5°C), anemia (HGB <100 g/L), total hospitalization costs, and surgery costs.
Statistical analysis
Categorical variables are presented as number/proportion (%) and were analyzed by the chi-square test. The Kolmogorov–Smirnov test was performed to determine normality of continuous variables. Data are shown as mean ± standard for normally distributed variables. If variables were normally distributed, the independent t-test was used for analysis. The Mann–Whitney U test was used for the analysis of non-normally distributed data and data are shown as the median (range). All statistical analyses and data processing were conducted by SPSS18.0 statistical software (IBM, Armonk, NY, USA). P values and 95% confidence intervals are shown for assessment of clinical indictors of patients with placenta previa and accreta. P<0.05 indicates that the difference was significant.