Placenta accreta

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Last update:

November 24, 2009

Authors:

Vincenzo Berghella

Key Points

Risk factors for placenta accreta include prior cesarean delivery; placenta previa; prior uterine surgery; prior myomectomy; prior D&Es; Asherman’s syndrome; submucous leiomyomata; maternal age ≥35years old; multiparity; smoking.
All patients with prior cesarean delivery and placenta previa should be assessed for ultrasonographic evidence of placenta accreta.
Complications of placenta accreta include (maternal) hysterectomy, injury to other organs, blood transfusion, DIC, infection, and death, as well as (fetal) PTB and SGA.
There are no trials to assess any interventions in the management of placenta accreta. There are benefits and risks for all three main approaches, which include attempting spontaneous placental delivery, planned hysterectomy, and expectant/medical management. While attempting placental delivery is the most common approach, planned hysterectomy may be offered if the diagnosis is highly suspected and the woman does not desire further fertility. Expectant/medical management should be considered only when the woman wants to preserve her fertility and no active uterine bleeding is present.

Diagnosis/definition

Placenta accreta is defined as a placenta which is abnormally adherent and sometimes invasive to the uterus, due to total or partial lack of the decidua basalis layer. The Nitabuch membrane, a fibrinoid layer that separates the deciduas basalis from the placental villi, is imperfectly developed. The antenatal diagnosis of placenta accreta can be suspected by history (especially prior cesarean delivery) or by ultrasound (table), but it is not 100% accurate by these methods (see below). Unfortunately, even the postpartum diagnosis is controversial. Postpartum histologic examination would require both placenta and uterus, and sample the whole interface, conditions that are almost never present. If only the placenta is examined histologically, usually the specimen is in pieces, only a few placental surfaces are sampled, and small areas that might contain myometrial tissue may be missed. So, in cases of clinically suspected placenta accreta, failure to demonstrate adherence or myometrial tissue the the maternal surface of the placenta can not always be used to the exclude this diagnosis.1 So there is no 'gold standard' for the diagnosis of accreta, which remains mostly a clinical diagnosis based on the clinician's impression of abnormally adherent placental tissue. . Moreover, incidental finding of placenta accreta at histologic examination is not uncommon.2

1. Jacques SM, Qureshi F, Trent VS, Ramirez NC, Placenta accrete: mild cases diagnoses by placental examination. Int J Gynecol Pathol 1996;15:28-33 [II-2]
2. Jacques SM, Qureshi F, Trent VS, Ramirez NC, Placenta accrete: mild cases diagnoses by placental examination. Int J Gynecol Pathol 1996;15:28-33 [II-2]

Epidemiology

1/2,500 deliveries (and increasing, as cesarean delivery rates increase).

Classification

Placenta accreta (vera): chorionic villi are attached directly, but do not invade, the myometrium
Placenta increta: placental villi invade the myometrium
Placenta percreta: placental villi invade beyond the whole myometrium, into the uterine serosa and possibly into adjacent organs (especially the bladder)

Risk factors/associations

Prior cesarean delivery (table 1).1 Most morbidity from repeat cesarean delivery derives from accreta and hysterectomy. Placenta previa; prior uterine surgery; prior myomectomy; prior D&Es; Asherman’s syndrome; submucous leiomyomata; maternal age ≥35years old; multiparity; smoking

1. Silver RM, Landon MB, Rouse DJ, Leveno KJ, Spong CY, Thom EA, et al. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol 2006;107:1226-32 [II-2]

Complications

Maternal: Hysterectomy, injury to other organs, blood transfusion, DIC, infection, death (<1-7%). Perinatal: PTB, SGA.1

1. Gielchinsky Y, Mankuta D, Rojansky N, Laufer N, Gielchinsky I, Ezra Y. Perinatal outcome of pregnancies complicated by placenta accreta. Obstet Gynecol 2004;104:527-30 [II-2]

Pregnancy Management

Prenatal care

Ultrasonography is the best test for the antenatal diagnosis of placenta accreta. Ultrasonographic signs of placenta accreta are shown in table 2.1 It is important to know that even the combinations of all these signs is not 100% sensitive and/or specific for the diagnosis for accreta. Most studies report sensitivity, specificity, positive and negative predictive values of about 80-90%. (20) Three-dimensional and power Doppler ultrasound have been insufficiently studied to be assessed adequately. Further evaluation of possible placenta accreta include MRI (especially T-2 and Short Tau Inversion recovery images), which may be informative especially for cases in which ultrasound is inconclusive, posterior previas and to assess possible bladder involvement.2 3 4 Cystoscopy can be considered in cases where bladder invasion is highly suspected by radiologic studies.

Preparations and Plans for delivery
If placenta accreta is suspected, appropriate counseling and preparations should be made. Multidisciplinary management is important. Labor and delivery staff should be notified regarding delivery plans and location, as well as nursing, surgery, anesthesia, neonatology, and blood bank staff. Interventions have not been tested in any trial, and so each intervention should be discussed with patients, making sure they understand that the interventions have not been clearly shown to improve outcomes and their utilization is not considered “standard of care.” Complications should be reviewed, as well as approach to management, with different options of attempt at placental delivery, planned hysterectomy, or expectant management. Additional preventive or therapeutic interventions as described below should be discussed, allowing patient input into management given lack of trials guiding management.
Pre-operative laboratory tests include at least type and crossmatch. Notify blood bank: blood products should be available in the OR at time of the procedure. Consider reserving cell saver for OR. Consider bowel prep: clear liquids day before procedure; fleets phospho-soda or fleets enema are options.
Notification of back-up consultants:

Anesthesia should be notified of possible need for massive transfusion, possible central monitoring.
Urology may be notified for possible cystoscopy, with possible placement of ureteral stents in OR pre-procedure, with standby for possible back-up.
CVIR (CardioVascular Interventional Radiology) may be notified for preoperative placement of uterine/ hypogastric artery catheters for potential postpartum embolization and/or balloon inflation. This intervention has not been studied in a trial, and even case-control studies do not confirm its efficacy.5
Gyn/Oncology or other experienced pelvic surgeon should be notified as possible back-up.

1. Chou MM, Ho ES, Lee YH. Prenatal diagnosis of placenta previa accreta by transabdominal color Doppler ultrasound. Ultrasound Obstet Gynecol 2000;15:28-35 [II-3]
2. Dwyer BK, Belogolovkin V, Tran L, et al. Prenatal diagnosis of placenta accreta. Sonography or MRI? J Ultrasound Med 2008;27:1275-81[n=32]
3. Warshak CR, Eskander R, Hull AD, et al. Accuracy of ultrasonography and magnetic resonance imaging in the diagnosis of placenta accreta. Obstet Gynecol 2006;108:573-81[n=453-largest series]
4. Palacios Jaraquemada JM, Bruno CH. Magnetic resonance imaging in 300 cases of placenta accreta: surgical correlation of new findings. Acta Obstet Gynecol Scand 2005;84:716-24 [n=300][II-2]
5. Levine AB, Kuhlman K, Bonn J. Placenta accreta: comparison of cases managed with and without pelvic artery balloon catheters. J maternal-Fetal Med 1999;8:173-6 [II-2]

Delivery

It is advisable to perform surgery in main Operating Room (OR) rather than labor and delivery. First start in the morning should be seeked. If done on labor and delivery OR, expect long operating time and therefore reserve at least two CD slots. The best gestational age for delivery of a woman with placenta accreta is unknown, but most authors recommend 36-37weeks with some consideration for the potential benefit of FLM amniocentesis. Some consider a course of steroids for elective cesarean delivery before 39 weeks. If patient accepts, arrange for 2 doses given 24 hours apart, with 2nd dose to be administered at least 24 hours before delivery. There are three potential approaches to managing placenta accreta after delivery of the baby by CD:

Attempt at delivery of placenta: In many cases, as accreta cannot be confirmed antenatally with 100% accuracy by radiologic studies, an attempt at spontaneous placental delivery is made. Creation of a bladder flap may be beneficial in case a hysterectomy is later necessary. Uterine incision should be made, if possible, away from the placenta, which therefore should be ‘mapped’ by ultrasound beforehand. Intra-operative ultrasound with a sterile cover over the probe placed on the exposed uterus may be helpful if preoperative ultrasound is not informative. If spontaneous placental delivery fails, the operator must decide if either manual placental removal in pieces or hysterectomy is the next intervention, based on several factors, including the degree of invasiveness and amount of bleeding. Areas of the placental bed which will bleed can be oversewn with sutures, but usually these are in the very low uterine segment and cervix, and often continue to bleed despite suturing or uterotonics. Ligation of blood supply is often not beneficial, given the high number of collateral vessels. Packing has been used as a temporary measure to control bleeding. Hysterectomy may be necessary if uterine bleeding cannot be controlled, hopefully BEFORE massive blood loss and cardiovascular instability. Given most bleeding is from the lower part of the uterus, usually total hysterectomy including the cervix is necessary. Gravid hysterectomy is associated with an incidence of maternal mortality of up to 7%, with a 90% incidence of transfusion, 28% incidence of postoperative transfusion, and a 5% incidence of ureteral injuries or fistula formation.1

Planned hysterectomy: If the diagnosis is highly suspected by history and radiologic studies (e.g. multiple prior cesarean deliveries, placenta previa, and several ultrasonographic findings of placenta accreta), and the woman does not desire further fertility (e.g. had requested tubal ligation), it might be prudent to deliver the neonate and proceed with hysterectomy while the placenta remains attached.2 In these controlled situations, maternal morbidity of gravid hysterectomy may be decreased, but fertility is lost.

Expectant or medical management: There are over a dozen reports of expectant or medical management of placenta accreta. The placenta is left in situ, with either no therapy or, most commonly, methotrexate therapy. Medical management should be considered only when the woman wants to preserve her fertility and no active uterine bleeding is present. The cord is ligated, and the uterus closed with the placenta in situ. Antibiotics prophylaxis is suggested given the risk of infection, and short-term uterotonics for postpartum hemorrhage prevention, but there are no trials on these interventions. Follow-up is done with serial ultrasounds (up to daily) to monitor involution and decrease in placental vascularity. Quantitative HCG should be monitored serially. If HCG levels plateau, or uterine size or placental vascularity do not decrease by 72 hours, methotrexate is usually given as 1mg/kg on alternate days for a total of 4-6 doses, or according to HCG levels and ultrasonographic findings.3 Women on methotrexate should be monitored with LFTs, platelet counts, and creatinine levels. Over 90% of the reports state successful outcomes, with future pregnancies and avoidance of gravid hysterectomy. In some cases, hysterectomy may be needed for late-occurring hemorrhage.

1. O’Brien JM, et al. The management of placenta percreta: conservative and operative strategies. Am J Obstet Gynecol 1996;175:1632-8 [II-2]
2. American College of Obstetricians and Gynecologists. Placenta accreta. ACOG Committee Opinion No. 266, January 2002 [review]
3. Hundley AF, Lee-Parrotz A. Managing placenta accreta. OBG Management 2002;8:18-33 [review]

Post-partum/breastfeeding

Consider reserving an intensive care unit bed.

Tables

Risk of placenta previa and/or accreta (and other complications) according to nu

Ultrasonographic signs of placenta accreta

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