Once a rare occurrence, placenta accreta is becoming an increasingly common complication of pregnancy, likely related to the increasing rate of cesarean delivery over the past two decades.1 Because the indications for cesarean delivery seem to be steadily expanding, including cesarean delivery on maternal request, the incidence of placenta accreta is likely to continue to increase.
Placenta accreta is defined as the abnormal presence of villi attached to the uterine myometrium. The etiology is associated with a defect in the decidua basalis, which allows villi to invade into the myometrium and occasionally into tissues beyond. The resulting abnormal implantation prevents the normal mechanisms of placental separation and hemostasis, resulting in massive, life-threatening hemorrhage, even when hysterectomy is performed. Blood loss after attempted placental removal has been reported to be greater than 3,000 mL in 90% of patients with placenta accreta.2 As many as 90% of patients require transfusion, and 40% require greater than 10 units of packed red blood cells.3 Maternal mortality with placenta accreta has been reported to be as high as 7%.2,3
Several risk factors for placenta accreta have been reported, including one or more prior cesarean deliveries and especially when there is coexisting placenta previa. In the presence of a placenta previa, increasing numbers of prior cesarean deliveries exponentially increase the risk of placenta accreta.4–7 Advanced maternal age, prior uterine surgery, and smoking have also been associated with placenta accreta.
We have previously reported our experience with the role of ultrasonography and magnetic resonance imaging in the diagnosis of placenta accreta.8 The purpose of the current study is to compare outcomes in patients with predelivery diagnosis of placenta accreta managed with planned cesarean hysterectomy and those in whom a predelivery diagnosis was not made. In all cases, the diagnosis was confirmed by pathologic examination of uterine/placental tissue.
MATERIALS AND METHODS
The study was approved by the University of California, San Diego Human Research Protection Program. The study population consisted of all women with placenta accreta confirmed pathologically after undergoing delivery at the University of California, San Diego Medical Center from January 1990 to April 2008. A confirmed diagnosis of placenta accreta required the pathologic demonstration of placental villi directly attached to the underlying myometrium, with absence of the intervening decidua basalis. We did not include cases of clinically suspected placenta accreta that were not subsequently confirmed with pathologic examination of the placenta and uterus. All cases were examined by a single pathologist (K.B.).
To assess the impact of predelivery diagnosis of placenta accreta on maternal and neonatal outcomes, cases were divided into those with (n=62) and without (n=37) a diagnosis of placenta accreta before delivery. Predelivery diagnosis of placental accreta was made after the finding of suspicious characteristics on ultrasonography in women with risk factors. These characteristics include loss of continuity of the bladder wall, placental heterogeneity with sonolucent spaces adjacent to the placental implantation site, lack of a hypoechoic border (myometrial zone) between the placenta and the myometrium, increased vasculature evident on color Doppler sonography, and bulging of the placental/myometrial site into the bladder. If the ultrasound findings were not considered definitive, magnetic resonance imaging was performed using gadolinium contrast intravenously. Magnetic resonance imaging findings considered diagnostic of placenta accreta included placental heterogeneity, mass effect of the placenta into the underlying bladder or extending laterally or posteriorly beyond the normal uterine contour, obliteration of the myometrial zone visible on initial uptake of gadolinium, and a beading nodularity within the placenta.9
Once the prenatal diagnosis of placenta accreta was made, all patients were offered planned cesarean hysterectomy without attempted removal of the placenta. The management protocol involved a multidisciplinary team including perinatology, gynecologic oncology, anesthesiology, interventional radiology, and neonatology. Cesarean hysterectomy typically was scheduled for 34–35 weeks of gestation after a 48-hour course of intramuscular betamethasone to enhance fetal lung maturity.
Depending on the extent of the placenta accreta and degree of involved vascularity, internal iliac balloon catheters were frequently placed preoperatively. Cesarean delivery was typically performed during regional anesthesia and, if placenta accreta was strongly suspected, the placenta was left in situ and general anesthesia was administered for the hysterectomy. The internal iliac balloon catheters were inflated to assist clearing the surgical field of blood only if significant bleeding was encountered. The majority of patients were observed in the surgical intensive care unit (ICU) for the first postoperative day, and longer if clinically indicated.
Data collected included maternal demographics, antenatal radiologic diagnoses, operative findings and complications, estimated blood loss, transfusions, operative time, and surgical complications involving bladder, ureter, and bowel injury. Estimated blood loss was obtained from review of operative reports. Exact quantities of blood products were recorded. Outcome data for both mother and infant, including ICU and neonatal ICU (NICU) admission, hospital days and postoperative complications were also obtained. Analysis was performed using SPSS 17 statistical software (SPSS Inc., Chicago, IL). Data not normally distributed was log transformed for analysis using parametric statistical tests and retransformed for presentation. Continuous variables were analyzed with the Student t test. Categorical variables were compared using χ2 or Fisher exact tests.
Between 1990 and 2008, 100 women with pathologically confirmed placenta accreta were delivered. Of these, 99 had complete medical records including information regarding predelivery diagnosis.
The incidence of placenta accreta steadily increased over the time period of the study (Fig. 1). The demographics of the overall cohort are presented in Table 1. More than half (53%) of the patients had two or more prior cesarean deliveries, whereas 15% had no prior cesarean delivery. Of the 15 women without a prior cesarean delivery, six had dilatation and curettage, three had myomectomy or septum removal, three had placenta previa alone, and three had no identifiable risk factors. Although most patients with placenta accreta had coincident placenta previa, a substantial number (27%) had either a low-lying anterior or a posterior fundal placental implantation. Distribution of risk factors for placenta accreta between those with and without predelivery diagnosis demonstrates a higher rate of uterine surgery, placenta previa, and percreta in those with predelivery diagnosis (Table 1).
Considering all women in the cohort, the mean operative time was 3±0.03 hours, and the estimated blood loss was 2,570±1.7 mL. Approximately three quarters required transfusion (with a mean of 5.4±2.1 units of packed red blood cells). One quarter of the patients in the series had a major surgical complication: bladder injury in 17%, ureteral injury in 6%, and bowel injury in one patient. Intensive care unit admission was required in 66%, with a mean hospital stay of 6.6±1.8 days.
Women in whom placenta accreta was recognized in advance of delivery demonstrated a significantly longer length of hospitalization (7.4±1.8 compared with 5.5±1.6 days, P=.01) but received fewer units of packed red blood cells (4.7±2.2 compared with 6.9±1.8, P=.02). The estimated blood loss was lower in those with predelivery diagnosis (2,344±1.7 compared with 2,951±1.8 mL, P=.053), but this trend did not reach statistical significance (Table 2). There were no differences in the rate of maternal ICU admissions or surgical complications. Of 62 women diagnosed before delivery, 22 (35%) required emergency intervention before the scheduled procedure for the following reasons: 18 for bleeding, one for premature labor at 31 weeks, and three for nonreassuring fetal heart rate. Only nine patients with predelivery diagnosis of placenta accreta were delivered beyond 36 weeks. Four of these patients required emergency deliveries for hemorrhage.
Compared with those without predelivery diagnosis of placenta accreta, those with a predelivery diagnosis demonstrated a higher rate of steroid administration (65% compared with 16%, P≤.001), neonatal admission to the NICU (86% compared with 60%, P=.005), and longer neonatal hospital stays (10.7±1.9 compared with 6.9±2.1 days, P=.006) (Table 3). There was no significant difference in the NICU length of stay, frequency of respiratory distress syndrome, need for intubation, or neonatal surfactant therapy.
Placenta accreta is a major contributor to maternal morbidity and mortality in the United States, reflecting the recent escalation in the cesarean delivery rate. The optimal management regimen has yet to be defined because of the paucity of outcome data in the present literature. This cohort is somewhat unique also because only cases with pathologically confirmed placenta accreta were included. Our data document lower hemorrhagic maternal morbidity when the diagnosis of placenta accreta is made before delivery. We schedule delivery of women with diagnosis of placenta accreta at 34–35 weeks to reduce the morbidity associated emergent hysterectomy, which frequently is performed at night with the patient hemorrhaging. Our data further demonstrate that this practice was not associated with increased neonatal morbidity (length of NICU stay, respiratory distress syndrome, and the need for surfactant administration or intubation). Overall length of neonatal (not NICU) stay was increased in neonates born to mothers with predelivery diagnosis but, because maternal length of stay was also increased, it may be that women with more complicated cases (higher rate of placenta percreta) may have required prolonged postpartum hospitalization, which may have contributed to the longer neonatal stay in this group.
Limitations of this study include those inherent to retrospective observational studies. We relied on operative reports to obtain information on blood loss. It has been demonstrated that surgeons often underestimate true blood loss associated with surgical procedures, and this could have impacted our findings. The time span of the study is both a strength and a limitation given that our imaging and surgical skills may have improved over the time period of our study.
Considering the available alternative therapies for placenta accreta, leaving the placenta in situ followed by methotrexate,10–15 placental embolization,16–18 or simply expectant management,19 few large cohorts are available to judge relative efficacy. Several case reports have demonstrated success with methotrexate in various dosing regimens.11–14 Timmermans et al20 recently reported 60 cases undergoing conservative management in which 26 had conservative management alone, 22 had methotrexate therapy, and 12 had embolization. The rates of failure were 15%, 23%, and 25%, respectively; 11 of 60 (18%) experienced infection, 21 of 60 (33%) had persistent vaginal bleeding, and 4 of 60 (7%) had disseminated intravascular coagulopathy. Conservative management that resulted in significant hemorrhage, infection, sepsis, and thrombosis has also been reported.11,15,21–24
Considering the existing case series, approximately 90% of patients with placenta accreta will require immediate hysterectomy when placental removal is attempted because of massive hemorrhage.2,25,26 However, there are few reports of outcomes associated with planned cesarean hysterectomy. The first, comparing planned and emergency hysterectomy, reported improved outcome with planned delivery as measured by blood loss, transfusion, and vital sign abnormalities.10 More recently, Sumigama et al27 reported 23 cases of placenta accreta, with the lowest blood loss occurring in those patients who underwent delivery with the placenta left in situ, closure of the uterine incision followed by embolization, and then planned hysterectomy 7 days later. Despite limited data, many experts currently recommend planned cesarean hysterectomy.28 With the advent of improved prenatal diagnosis, our center has moved toward planned cesarean hysterectomy with the placenta left in situ. Prenatal diagnosis allows for preoperative management using a multidisciplinary approach, such that prenatal diagnosis alone was associated with decreased blood loss. Furthermore, after prenatal diagnosis of placenta accreta, a planned cesarean hysterectomy with the placenta left in situ was associated with significantly decreased hemorrhagic morbidity (blood loss and transfusion requirements).
The optimal timing of delivery of the patient with placenta accreta remains controversial. Results from the current study support the view that patients with a high diagnostic suspicion of placenta accreta can be delivered by cesarean hysterectomy at 34–35 weeks without significant increase in neonatal morbidity. This relatively early delivery timing, compared with the typical timing for uncomplicated placenta previa (approximately 37 weeks) may be justified by the complexity of the surgery, which is more difficult to orchestrate on an emergency basis. O’Brien et al3 reported that after 35 weeks, 93% of patients with placenta accreta experience hemorrhage necessitating delivery. In addition, despite high attrition rates before 36 weeks for indicated deliveries, four of eight maternal deaths occurred beyond 36 weeks.3 In our cohort, nine patients with prenatal diagnosis were scheduled for delivery at or after 36 weeks, and of these patients, four required earlier intervention because of maternal hemorrhage.
Based on the data of this study, prenatal diagnosis seems to be a key factor in optimizing the counseling, treatment, and outcome of patients with placenta accreta. Any woman at risk for placenta accreta (placenta previa, prior cesarean delivery, or prior uterine surgeries) should undergo careful imaging to assess for the presence of a placenta accreta in a center experienced with evaluating invasive placentation. Given the complexity of the surgical team necessary to optimize outcome and the increasing rates of hemorrhage before delivery in advancing gestation, early delivery should be recommended to patients when there is reasonable certainty regarding the diagnosis of placenta accreta.
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© 2010 by The American College of Obstetricians and Gynecologists.
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