Our study demonstrated that placenta previa on a cesarean scar termed as PPP is an extremely dangerous condition associated with pregnancy. Patients with PPP were associated with increased risks of maternal morbidity and adverse neonatal outcomes.
Overall, the incidence of postpartum hemorrhage in our cohort is 38.3% and 23.5% of patients required blood transfusions >4 units. It is well established that women with PAS disorders are highly related to massive blood loss, which may cause serious complications such as multisystem organ failure, disseminated intravascular coagulation, caesarean hysterectomy, preterm delivery, and even death[3]. In a large retrospective cohort study[4] including all hospital deliveries in Canada (excluding Quebec) for the years 2009 and 2010 found that approximately 50% of the patients with placenta accreta experienced postpartum hemorrhage more than 500ml, and 22.6% experienced a severe form of postpartum hemorrhage defined as postpartum hemorrhage with blood transfusion, hysterectomy, or other procedures to control bleeding).
Several risk factors have been evaluated to be contributable to PAS disorders[5]. However, placenta previa and previous cesarean delivery are the most acknowledged reasons for PAS disorders. A national case-control study in the UK conducted by Kathryn E. Fitzpatrick et al[6] demonstrated that PAS disorders occurred in more than 5% of women with both a previous caesarean delivery and placenta praevia, whereas the estimated incidence of PAS disorders was only 0.017% in all population; In a large prospective observational cohort study, Robert M. Silver et al[7] found that the risk of placenta accrete which is a form of PAS disorders increased with higher numbers of prior cesarean deliveries in woman with placenta previa, the risk of accreta was 3%, 11%, 40%, 61%, and 67% for first, second, third, fourth, and fifth or more cesareans, respectively. Our research is consistent with the previous analyses. Though PAS disorders are not included in the diagnosis of PPP, it is striking that PAS disorders occurred in more than half (63%) of patients in our cohort. Not surprisingly, women with PAS disorders are more likely to experience postpartum hemorrhage in our cohort. However, using the same criteria, it is noteworthy that the incidence of postpartum hemorrhage in this study without PAS disorders is still 13.1% and nearly two-fold higher, compared with the incidence of postpartum hemorrhage in patients with simple placenta pravia, which were reported to be 7.1% by Martina Kollmann et.al[8].
The best treatment strategy for PAS disorders remains a matter of debate. Most studies[9,10] showed improved outcomes with planned cesarean hysterectomy before the 35th gestational week. However, hysterectomy is extremely unpopular in China and most patients strongly wish to preserve uterus at any cost. Numerous studies[11,12] showed that conservative approach (with or without partial resection of placenta) was a uterus-preserving option for patient with PAS disorders. Nevertheless,PAS disorders managed with the placenta left in situ require close follow-up monitor and it takes at least several months after delivery before placental resorption was achieved[13]. Moreover,maternal morbidity and mortality is not rare in the placenta left in situ approach[14]. In our study,all the cases were performed cesarean section with the removal of placenta at the same time initially. When a catastrophic bleeding occurred which is judged by the obstetric clinicians,subsequent hysterectomy was undertaken immediately. In contrast with the reported uterine preservation rate ranged from 78% to 87%. Uterine preservation rate was 97.3% in our cohort. The maternal morbidity is also unremarkable. Bladder invasion were encountered in 4 patients, and reconstruction of the bladder was preformed successfully. No death case was reported. This finding suggests that extirpative management could be an option for patients with PPP who have an excessive desire for future fertility.
Given the possibility of massive blood loss, emergency cesarean was performed directly if preterm labor and vaginal bleeding occurred. Preterm delivery complicated 63.4% of patients in our cohort due to antepartum bleeding. Contrary to previous studies[15], there was no association between emergent delivery and postpartum hemorrhage or large volume transfusion in our cohort. Since an early delivery may expose a neonate to prematurity complications. Delivery may reasonably be delayed in asymptomatic patients with PPP to improve neonatal outcomes. However, it must be recognized that all of the patients in the present study were treated at a tertiary center with intensive support services and the management which may not be applied to smaller facilities that lack these services.
We recognize several limitations in our study. The first is its retrospective design and limited cases included were from a single institution. The selection bias was not likely avoided. However, given the infrequency of PPP, a prospective study consisting large number of subjects is difficult to perform and take several years. To our knowledge, few studies[16] have concentrated on patients with PPP in the literature, our study is helpful to the understanding of characteristic of this condition. Second, the post-operation following up is incomplete and not long enough. Thus, the complications associated with PPP and surgery were probably underestimated. Moreover,length of the observation period was unlikely to evaluate the future fertility. Third, all the subjects were managed in our hospital which is a tertiary care center. massive blood transfusions, anaesthesia and subspecialists in neonatology, urology, vascular surgery, and gynecological oncology were readily available. Accordingly, results may not be generalizable to smaller rural hospitals, and our data likely underestimate the actual risk in smaller hospitals without special services. Finally, we lacked data on some important variables, including BMI, prior uterine surgery history, smoking during pregnancy, medical and obstetric risks such hypertension, diabetes. It is possible that these variables may influence the pregnancy outcomes in PPP and need further evaluation.
In conclusion, PPP is associated with considerable maternal and fetal morbidity, particularly in patients with comorbid PAS disorders. Delayed delivery may be warranted for those without meaningful vaginal bleeding and preterm labor but need further prospective clinical trials to confirm.