29The Management of Placenta Accreta atQueen’s Hospital, Romford, UKM. O. Thompson, C. Otigbah, A. Kelkar, A. Coker, A. Pankhania andS. Kapoor

GENERAL COMMENTS

Introduction

Placenta accreta, increta and percreta are all forms ofmorbidly adherent placenta (MAP) with abnormallyinvasive placentation. Histologically defined bytrophoblastic invasion of the myometrium in theabsence of intervening decidua, superficial myometrialinvasion is classed as accreta, deeper myometrialinvasion as increta, and invasion through the serosa orinto adjacent pelvic organs as percreta1. The conditionwas of such rarity 60 years ago that many experiencedpracticing obstetricians had never encountered acase, and the associated maternal mortality ratewas extremely high (37–67% of cases managed)2.Although associated maternal mortality is now signifi-cantly lower (7–10% of cases)3,4, it remains a muchdreaded obstetric complication primarily because ofthe risk to the mother. Although awareness of thecondition and its attendant risks is increasing, no con-sensus exists regarding the best management strategiesto maximize outcomes. This paucity of informationhampers service planning and decisions on optimalmanagement strategies and presents difficulties in con-ducting meaningful research, particularly comparativestudies (see Chapter 1).

Clinical significance

Women with placenta accreta or any of its variants areat high risk of life-threatening massive obstetric hem-orrhage, bladder or ureteric injury, uterine perforationand rupture, peripartum hysterectomy and maternaldeath1. The prevalence is apparently on the increaseglobally due to the increasing cesarean delivery ratesand advancing maternal age5. Reported prevalence inthe 1930s was less than 1 in 30,000 deliveries, increas-ing to 1 in 2510 deliveries in the 1980s and up to 1 in540 deliveries as reported in some centers by 20065,6.

Local significance

The Maternity Unit at Queen’s Hospital, Romford,is the high-risk section of one of the largest acute

hospital trusts in the UK, with an average annual deliv-ery rate of 10,000 births. The Trust serves a populationof 750,000 from a wide range of social and ethnicgroups. Active screening for MAP commenced after amaternal death from a morbidly adherent placenta in2006. In the subsequent 4-year period, a positive ante-natal diagnosis was made in 17 of the 39,120 pregnan-cies. There was one false positive diagnosis, giving anannual prevalence of 1:2445 deliveries for MAP. Thischapter reviews the medical literature on MAP anddraws on the experience provided by these cases.

Diagnosis

Traditionally, a diagnosis of MAP was made eitherclinically following difficult or failed attempts at man-ual placental removal of a MAP or histopathologicallyfollowing peripartum hysterectomy or autopsy (Figure1). In our unit, as is the case in many centers world-wide, antenatal diagnosis is now increasingly madeusing a combination of ultrasound and magneticresonance imaging (MRI).

Diagnosis of a MAP in the first trimester is exceed-ingly rare. It is usually encountered acutely followingunexpectedly severe uterine bleeding duringpregnancy7, termination or evacuation of retained

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Figure 1 Histological slide showing placenta accreta

products of conception. Some cases present withheavy genital tract bleeding a few weeks or monthsafter the evacuation of a spontaneous, missed orincomplete miscarriage and the diagnosis of a retainedplacenta accreta, increta or percreta is made only afterhistological examination following surgery8–10.

Currently, most cases are detected in the second tri-mester, although the diagnosis may remain inconclu-sive until the later stages of pregnancy if or when thereare no symptoms of vaginal bleeding to prompt earlierinvestigation. When vaginal bleeding occurs early onin the first and second trimesters, however, near-catastrophic blood loss is the usual result in most cases.As a consequence, there have been calls to commenceultrasound screening for MAP early, as part of the11–14 week nuchal translucency screening scan11,12.Indeed, close scrutiny of the uterine wall, umbilicalcord insertion and placentation at the 11–14 weekultrasound screening may be helpful in establishing adiagnosis of MAP at such early gestations.

Risk factors

The commonest etiologic factors seen with MAP are aprevious endomyometrial injury in conjunction with alow lying placenta13. Women with placenta previa anda previous cesarean delivery are now well established asbeing at greatest risk for MAP14. Screening for MAP istherefore possible by combining the previous obstetrichistory with a thorough ultrasound examination of theplacenta. In women who are found to have placentaprevia on ultrasound, the association with previouscesarean section delivery is strong, and the risk of MAPincreases from 24% with one previous cesarean to 67%with three or more previous cesareans15. Other impor-tant associated factors include a short birth interval fol-lowing a cesarean delivery16,17, increasing parity andadvancing maternal age above 35 years1.

Biochemical markers

Biochemical detection is not established for MAP.However, elevated maternal serum levels of α feto-protein (AFP) and serum free β human chorionicgonadotropin (β hCG) have been reported with MAPin the absence of fetal abnormality18–20. The rationaleis probably similar to other conditions where a breachor leak occurs at fetoplacental–maternal interfaces,although the elevation in AFP is postulated to be morelikely related to coexisting placenta previa21. Anelevated level of creatine kinase, possibly secondaryto an endomyometrial breach or increased breakdown,is also reported as a possible marker20,22. More sophis-ticated laboratory tests, including the possibility ofantenatal diagnosis from fetal cells in maternal bloodare being studied23.

Ultrasound imaging

Grayscale ultrasound is the mainstay of antenatal diag-nosis with a high sensitivity and specificity. Multiple

ultrasound diagnostic signs are usually seen in caseslater confirmed to have MAP, and, although there isno single pathognomonic feature, most have a strongassociation. The greater the number of characteristicultrasound features seen, the more likely is the diagno-sis24, and there may be an increase in the number andclarity of diagnostic ultrasound parameters as gestationincreases. Although the superiority and accuracyof one route over another is often debated, thetransabdominal and transvaginal routes are oftencomplementary.

Our personal observations suggest that the moresevere and extensive the morbid adherence, the easierthe antenatal ultrasound diagnosis. Ultrasound appear-ances, however, do not always accurately predict theclinical severity of bleeding, as perforation and torren-tial bleeding remain possible, occurring even withsmall or focal lesions. Ultrasound imaging has a goodnegative predictive value for the diagnosis of MAPranging between 92 and 98%, a fact which is invalu-able in any good screening program25,26.

Characteristic findings for MAP on grayscale ultra-sound include:

(1) The presence of lacunae;

(2) Loss of the normal hypoechogenic retroplacentalmyometrial zone;

(3) Irregularity of the retroplacental sonolucent zone;

(4) Thinning, especially less than 1 mm, or disruptionof the uterine serosa–bladder interface;

(5) The presence of focal exophytic masses;

(6) Lacunar flow within the placenta25,27 (Figure 2).

Color Doppler ultrasound

The use of color Doppler can improve the accuracyof diagnosis of MAP by providing a more detailedassessment of the depth of trophoblastic invasion intothe myometrium or serosa, especially in an anteriorplacenta28–30. The sensitivity and specificity of color

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Figure 2 Grayscale image showing presence of lacunae

Doppler in diagnosing placenta previa accreta rangebetween 82.4 and 100% and 92 and 96.8%,respectively31. A finding of color Doppler flow withinlacunae further increases diagnostic sensitivity to100%, with an associated 83% positive predictive valuefor morbid placental adherence28.

Characteristic findings on color Doppler ultrasoundinclude:

(1) A diffuse lacunar flow pattern with high-velocitypulsatile venous-type flow (peak systolic velocitymore than 15 cm/s) spread throughout theplacenta, myometrium and cervix;

(2) A central lacunar flow pattern with turbulentflow distributed regionally or focally in theparenchyma;

(3) Bladder–uterine serosal interphase hypervascularity;

(4) Markedly dilated vessels over the peripheralsubplacental zone;

(5) An absence of subplacental vascular signals inthe areas lacking the peripheral subplacentalhypoechoic zone;

(6) Abnormal vascular channels linking the placentato the bladder31 (Figure 3).

Three-dimensional ultrasound

It is unclear whether three-dimensional ultrasono-graphy adds any benefit to diagnostic accuracy forMAP29. However, viewing planes can be more easilymanipulated to enhance views of the vascular frame-work of the placenta and adjacent tissues, thus improv-ing detection of bladder and parametrial extension.Four-dimensional ultrasound, on the other hand,permits instantaneous multiplanar reconstructions inreal time. This gives an added ability to display androtate reconstructed images from any desired angle,and from any of the three planes: sagittal, coronal, oraxial (Figure 4).

Three-dimensional color power Doppler ultrasound

The role of three-dimensional color power Doppler isbetter established. Color power Doppler ultrasound isreportedly the most sensitive and specific single crite-rion (sensitivity 97% and specificity 92%), with thehighest positive predictive value currently reportedfor diagnosis24,32 (Figure 5). This is the single mostreliable diagnostic modality and it increases diagnosticconfidence in determining the exact site, depth andextent of invasion. Characteristic findings on three-dimensional color power Doppler ultrasound include:

(1) Numerous dilated and coherent vessels involvingthe serosa–bladder interface on a basal view;

(2) Increased intraplacental hypervascularity;

(3) Inseparable cotyledonal and intervillous circula-tions;

(4) Tortuous vascularity with chaotic branching;

(5) Detour vessels on the lateral view24,32 (Figure 6).

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Figure 3 Color Doppler image of placenta increta

Figure 4 Three-dimensional color Doppler image showingplacenta percreta

Figure 5 Color power Doppler image of placenta increta

Magnetic resonance imaging

MRI is an imaging modality that does not require theuse of ionizing radiation, provides excellent tissue def-inition and additionally allows multiplanar imaging.MRI is increasingly useful in planning surgery,particularly in the evaluation of posteriorly sitedplacentas, in obese women and in pregnancies compli-cated by a reduced amniotic fluid volume, althoughclaustrophobia in some women may limit its use33–36.The additional use of an image enhancing contrastmaterial such as gadolinium is controversial because ofthe maternal and fetal risks, but this has been used incircumstances where the benefits of an accurate diag-nosis appear to far outweigh potential complications.MRI is a valuable diagnostic tool for MAPs with agood negative predictive ability. Characteristic MRIfindings include lower uterine segment thinning, protrusionsfrom the uterine wall, heterogeneous signal intensity withinthe placenta and dark intraplacental bands on T2-weightedimaging33–37 (Figure 7).

Screening for morbidly adherent placentas

The role of screening for MAP has yet to be estab-lished, even though a more widespread use of thismodality would offer clear advantages. In our unit,screening commenced in 2006, using the antenatalbooking history and ultrasound as the starting pointsfor our search. Any woman with a history of previousuterine surgery receives a thorough placental assess-ment at the 20 week second trimester ultrasound scanby a sonographer. A check is made for the diagnosticpointers described above and, if any positive findingsare present, the woman is referred to the fetalmedicine unit for a consultant’s assessment. Whererequired, an MRI scan is performed at 32 weeks’ ges-tation to help confirm or reject the diagnosis. A diag-nosis made in the third trimester is usually conclusive,and adequate preparations for a safe delivery can begin.

Management of morbidly adherent placentas

The most important aspects of management are:

(1) The early identification of women at high risk ofMAP;

(2) Intensive multidisciplinary care;

(3) Care and delivery in an appropriately equippedunit.

The care of women diagnosed at any stage of preg-nancy with MAP should be conducted by obstetriciansworking as part of a multidisciplinary team. In our unittwo senior obstetricians specialized in fetomaternalmedicine supervise the care of women with a diagno-sis of MAP. This ensures that routine pregnancy assess-ments and care are not ignored as a result of theoverriding concerns about the risks of placental bleed-ing. In the 5-year period since screening commencedand our multidisciplinary care team was constituted,we have now encountered 23 cases exhibiting theentire spectrum of MAP across the gestational range.

Planned management in antenatally diagnosedcases

After the antenatal diagnosis of MAP, a multidisciplinaryteam is assembled. Ideally the team should includespecialist obstetricians, anesthetists, urologists, inter-ventional radiologists, hematologists, neonatologists,blood transfusion specialists, operating department prac-titioners, portering staff and theater nurses and assistantstrained to assist in performance of cesarean hysterectomyand laparotomy, along with a full complement ofgynecological, vascular surgery and urology instruments.In reality, this list needs to be modified to comply withlocal needs, requirements and resources.

At Queen’s Hospital, Romford, because of thelevel of risk involved, emergency contact telephonenumbers for the delivery suite and senior specialistobstetric team are provided to the woman and herfamily with 24-hour availability of at least one senior

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Figure 6 Three-dimensional power color Doppler image ofplacenta increta

Figure 7 MRI scan showing placenta increta

member of the obstetric team. Details of her diagnosis;the grade and extent of morbid adherence; possiblerisks and complications to mother and baby; mode,details and risks of planned conservative or extirpativemanagement; the likely need for transfusion withblood products; cystoscopy; ureteric stenting; arterialembolization in the interventional radiology theatersuite; selective arterial ligation; planned abdominalincision, type of cesarean section planned; and type ofhysterectomy planned are all documented in the hos-pital antenatal hand-held records. An agreed, signedbirth plan with all these details boldly marked on therisk assessment page is also attached to the woman’shand-held hospital notes for contingency reasons.

Counseling

Counseling the woman and her family is crucial and isundertaken primarily by obstetric members of theteam who are the point of first contact. The gravity ofthis condition often dictates prolonged and detaileddiscussions with multiple family members present inorder to ensure a clear understanding. We, thereforehold our discussion sessions in the Fetal Medicine Unit(FMU) counseling room separately, and apart from theroutine antenatal clinic sessions for this purpose. Afterthe initial counseling sessions, a definitive manage-ment plan is agreed in consultation with the womanand her family by the 32nd week of pregnancy whenthe diagnosis would have been confirmed by theultrasound and MRI examinations.

Counseling includes advice to refrain from sexualintercourse until after delivery, to ensure that thewoman is not left unattended or on her own at home,and to arrange ambulance transfer to hospital immedi-ately if vaginal bleeding occurs. Advice is also given toreport any genital tract discharge, hematuria, abdomi-nal pain or uterine contractions to hospital immedi-ately via the delivery suite emergency telephonehotline. Ambulance services can then be contacted byour midwifery staff or directly via a telephone callfrom the woman to arrange hospital transfer.

It must be ascertained that the woman lives withineasy commuting distance of the hospital and that therehave been no prior episodes of vaginal bleeding orother complications before agreeing to outpatient carefollowing the diagnosis. The plans for operative deliv-ery, possible need for blood transfusion, uterine pres-ervation and hysterectomy are discussed in detail withthe woman and her relatives before the third trimesterand any concerns regarding these are thoroughly dis-cussed. All the discussions are carefully recorded in thehospital notes. Women who live more than 10 milesfrom the hospital are either managed as inpatients orreferred to their local hospital with all their results todate and a copy of the plan of care and delivery.

Consent

Consent for surgical treatment options should beobtained early, soon after the diagnosis, because of the

risk of urgent radical operative intervention before theend of the second trimester or emergency pretermdelivery. The consent form we use details the plannedconservative or extirpative management, associatedrisks and complications, need for transfusion withblood products, preoperative cystoscopy, uretericstenting, arterial embolization in the interventionalradiology theater suite, selective arterial ligation,planned abdominal incision, type of cesarean sectionplanned, and type of hysterectomy planned withextirpative management. This is individualized, withthese details entered manually on the routine NationalHealth Service operation consent form.

Coordination

Antenatal care and multidisciplinary team coordina-tion is handled by the FMU consultant obstetricians,a designated senior midwife and blood transfusionspecialist practitioners who all liaise closely with eachother and inform and update other team membersregularly. Close monitoring for any other incidentalpregnancy associated complications continues underthe care of the specialist obstetricians. Serial ultrasoundscans to assess fetal growth and maternal assessmentsare arranged at 24, 28 and 32 weeks of gestation. Theanesthetic and neonatology team members areinvolved once viability has been attained.

Gestational age at delivery

This is decided upon on an individual basis dependingon the risk to the mother including severe maternalgenital tract bleeding, any associated medical orobstetric conditions, fetal status and available facilitiesfor neonatal intensive care. Timing of delivery isdiscussed at 32 weeks with the multidisciplinary team.In the absence of significant antenatal complications,delivery is usually aimed for 37 weeks’ gestation. Earlytransfer to an appropriate unit should be arranged ifappropriate local facilities for neonatal care are deemedsuboptimal.

Multidisciplinary team involvement and planning

Preoperative review

A multidisciplinary team review is held at 32 weekswhere clinical status of both mother and baby, allimaging, hematology and other test results are dis-cussed, and the plan for delivery is reassessed with anynew findings. A diagnosis of parametrial invasion isparticularly important in planning surgery37. Thisis assessed antenatally using three-dimensional colorDoppler ultrasound and MRI at 32 weeks to enableplanning of the surgical technique at the multi-disciplinary team meeting with the team’s inter-ventional radiologists, urologists and obstetricians.

The final multidisciplinary review takes place in theweek before delivery, usually between 34 and 36weeks. An evaluation of the items listed in Figure 8 is

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performed and each item is crossed off the checklistonce dealt with. At this stage decisions are takenregarding the team members required to attend thedelivery, the sterile packs required, which operatingtheater is to be used and the theater staff who willattend. In order to allow ample time and preparationfor the delivery and after care the number of casesbooked for other elective surgery in the delivery suitetheaters on that morning is curtailed.

Pre-delivery specialist anesthetic reviews arealso arranged to decide on the anesthetic plan in con-sultation with the woman in time for discussion at thismeeting along with the neonatology review.

The hematology team members are closelyinvolved in antenatal care; any pre-existing anemia iscorrected where possible prior to delivery, and allwomen who decline blood products are identified toexplore means of boosting their hemoglobin levels,avoid excessive blood loss and identify what bloodproducts, if any, they would accept under emergencylife-threatening conditions (Chapter 72). This isparticularly important because even minimal bloodloss in an anemic or undernourished woman couldhave more profound consequences38.

This activity is especially valuable in developingcountries where access to blood transfusion facilitiesmay be quite a distance away, thereby necessitatingearly referral and transfer to an appropriate center forhospital-based care until delivery.

Women with a previous cesarean delivery andplacenta previa or antenatally suspected morbid pla-cental adherence should be delivered in units where atleast a level 2 critical care bed is available. For womenwho decline blood products, transfer to delivery unitswhere cell salvage and interventional radiology areavailable is recommended39. Women living in devel-oping countries or in areas where no surgical or bloodtransfusion services are available should be transferredearly to secondary or tertiary units where theseexist38,40.

MANAGEMENT OPTIONS

The definitive treatment strategy for MAP is eitherconservative or extirpative, with the surgical removalof the placenta, uterus or both. Overall, the planned

management depends on the degree of placental inva-sion and the woman’s desire to retain her reproductivecapacity.

Conservative management

Conservative management is defined by uterinepreservation and retention of fertility. Various conser-vative management methods are described, but, ingeneral, the practice is either to undertake manual pla-cental removal immediately after the delivery of thebaby or to proceed with planned placental retention,awaiting either spontaneous expulsion or resorption.In some case reports, manual placental removal hasbeen undertaken after a delayed interval to permitregression of the vascular supply. In other reportedcases, immediate placental morcellation, curettage orremoval piecemeal followed by the insertion of a uter-ine pack, uterine tamponade device, balloon catheteror the application of uterine hemostatic or compres-sion sutures have been successful2,41–47.

Other semiconservative interventions, improvizedon the spur-of-the-moment in critical emergency situ-ations to avoid further bleeding complications or moredrastic surgery are reported. These include oversewingof the placental bed, or suturing flaps of cervix orsurgical mesh to cover defects41,48.

In cases presenting acutely in the first or secondtrimester, simple excision and repair of defects causedby the implantation, curettage or removal followed byinsertion of a tamponade balloon49, hysterotomy andevacuation of products or, rarely, wedge resection andrepair of myometrium have been reported48,50.

Those presenting acutely in the third trimester aremore often seen during the third stage of labor, afterthe delivery of the infant. The commonest presenta-tion is of a retained placenta with the finding of anabsent cleavage plane for its safe removal. Conservativemanagement under these circumstances involves leaving theentire placenta in situ for removal later or awaiting spontane-ous complete resorption.

The woman is carefully counseled about the find-ings and her risks, and closely followed up weekly forat least 6 weeks with regular clinical and ultrasoundexaminations, monitoring her white cell count anddifferential along with inflammatory markers such asC-reactive protein to assess for signs of infection.A broad-spectrum prophylactic antibiotic such asamoxicillin and clavulanic acid is given for 10 days.

Complications have been reported with the conser-vative management of MAP. These include immedi-ate to late postpartum vaginal bleeding up to 3 monthsafter delivery which could result in disseminatedintravascular coagulation (DIC), infectious morbidity,fever secondary to tissue necrosis, prolonged retentionof products of conception and placental polyps.Rarely, vesicouterine fistulas or urethral strictures mayoccur from placental necrosis secondary to placentapercreta44,46. There is no respite until the placenta iscompletely reabsorbed or expelled and at the 6 week

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Checklist for 32-week multidisciplinary team meeting Details

1. Operation consent forms

2. Planned anesthesia

3. Choice of abdominal incision

4. Planned uterine preservation

5. Planned placental retention

6. Anticipated parametrial or paravesical dissection

7. Anticipated interventional radiology procedures

8. Anticipated blood transfusion requirements

9. Any concurrent medical or obstetric complications?

Figure 8 Morbidly adherent placenta (MAP) multidisciplinaryteam management checklist

follow-up visit the histopathology findings should bereviewed.

In acutely presenting cases postpartum wherethere is continued or heavy bleeding, radiologicalembolization or selective surgical arterial ligationof the internal iliac and uterine arteries should bearranged immediately. In some instances, the placentais then expelled shortly afterwards, within 48 hours to6 weeks, although it may take up to 6 months andsometimes over a year for the placenta to be entirelyreabsorbed46. If bleeding does not cease, despite utero-tonic administration and arterial occlusion, uterineballoon tamponade, or uterine compression suturesshould be tried49,50.

True MAPs do not undergo complete spontaneousseparation from the uterine wall in the third stage,leading to significant attendant risks of secondary hem-orrhage, infection and the need for a hysterectomy at alater time. An awareness of these risks has motivatedthe introduction of interventions to attempt to hastenplacental involution. These include reducing bloodsupply to the uterus through transcatheter arterialembolization, selective surgical arterial ligation orstepwise devascularization50–54. Attempts to expediteresorption by inducing placental necrosis using cyto-toxic therapy, especially methotrexate, are also wellreported in the literature55–58.

Methotrexate efficacy is not well substantiated, andno standard mode of administration, treatment dosagesor protocols exist. Moreover, reports of failed conser-vative management associated with its use exist56,57,as do reports of maternal mortality associated withlow dose administration for ectopic gestations or withintraumbilical cord injections59,60. Because successfulconservative management without the use ofmethotrexate is now reported46, it may be advisableto refrain from its use as an adjunct. In our unitadjunctive methotrexate in the treatment of MAPwas discontinued following catastrophic complicationsassociated with a maternal death secondary tofulminant sepsis and tissue necrosis.

Radiological transcatheter pelvic arterialembolization, on the other hand, is reportedly moreeffective with conservative management62, althoughits prophylactic value is still debated and repeatembolizations may have to be performed63. There areno known randomized controlled trials of the use ofarterial embolization in the management of MAPs.A review conducted for the World Health Organiza-tion in 2009 concluded that although there may beresource issues, it should be considered a recom-mended intervention for the control of obstetrichemorrhage where readily available38.

The various adjunctive measures described aboveare used to prevent, reduce or treat the massive obstet-ric hemorrhage associated with placental retention orremoval, and each is discussed fully in the pertinentchapters. In the context of MAPs, the usual primary causeof dangerous vaginal bleeding is attempted manual removalwhich at any stage is fraught with danger and should bestrongly resisted64,65.

Extirpative management

Extirpative management could be conducted as eitheran emergency or electively, and is characterized byremoval of the placenta and the uterus64. Althoughsurgery can be performed immediately, it may need tobe deferred depending on the type of presentation andclinical status, to undertake planned placental reten-tion with or without an adjunctive modality, followedby an interval hysterectomy.

Emergency management in acutely presentingcases

Management of MAP presenting acutely in the firstand second trimesters is individualized according tothe mode of presentation, maternal condition andseverity. Definitive management includes hemo-dynamic stabilization with immediate fluid and bloodreplacement, followed by diagnostic imaging in theform of an emergency ultrasound, computed tomo-graphy (CT) or MRI scan when the woman ishemodynamically stable. Based on the results of thescan, the presence or absence of hemoperitoneumand the woman’s clinical condition, an operativeprocedure is planned. As the risk is very high in thosepresenting at earlier gestational ages, consent forsurgery should always include permission for ahysterectomy.

In cases presenting in the third trimester, theplacenta should also be left undisturbed while prepara-tions are quickly made for surgery. The intraoperativefindings dictate the mode of treatment. A hysterec-tomy is the treatment of choice in most severe cases,while selective radiological arterial embolization orother hemostatic methods may be useful in facilitatingsurgery and arresting hemorrhage. In desperate cases,aortic compression may be required to control uterinebleeding and can be done safely for up to 4 hours untilit is controlled or help becomes available65.

A primary decision required with extirpative man-agement is whether to perform an immediate or inter-val hysterectomy. It also has to be decided whether atotal or subtotal (supracervical) hysterectomy is moreappropriate. A subtotal hysterectomy is more expedi-ent particularly in moribund cases, but a total hysterec-tomy with removal of the cervix is advocated by somesurgeons because of concerns about delayed hemor-rhage from the hypervascularized vault especially incases of placenta previa accreta.

In practice, the decision is often best taken intra-operatively based on the patient’s physical condition,the degree of distortion of the pelvic anatomy byplacental infiltration or scarring from previous surgeryand the severity of bleeding. Surgical skill and experi-ence significantly influence the decisions because ofthe distorted anatomy that often accompanies morbidplacental adherence, and situations may arise where asubtotal operation is preferred because of the woman’sclinical status, or limited operator experience. Inter-ested readers should consult Chapter 31.

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Elective management in antenatally diagnosedcases

Since commencing our screening program, the vastmajority of cases presenting in our unit are nowdiagnosed prior to the late second trimester andare delivered electively in the daytime when properarrangements for major operative interventions can bemade. This helps to prevent major complications suchas those described above.

Immediate preoperative preparation

The equipment and supplies checklist (Figure 9) isreviewed the day prior to surgery, and the blood trans-fusion specialist practitioner checks hematology andblood bank supplies. On the morning of surgery, thewoman is admitted from home after an overnight fastor is transferred from the antenatal ward if alreadyadmitted, and the consent forms and theater checklistare reviewed once again.

The color Doppler and MRI findings accuratelypredict the need for preoperative ureteric stenting37,a fact which has been our experience during the past5 years. If required, intravascular balloon embolizationcatheters are inserted in the interventional radiologytheater suite, before the woman is transferred to thedelivery suite operating theater with the cathetersready in place. The preoperative checklist is thenreviewed.

Preoperative placental site mapping is performedwith a review of the ultrasound and MRI scans by theurologist, interventional radiologist and obstetriciansto identify areas of potential difficulty with dissection,areas of particular hypervascularity and, very impor-tantly, specific areas of parametrial, inferolateral pelvicor bladder extension. An ultrasound scan can be per-formed intraoperatively to map the placental coveragearea using a sterile probe cover. At Queen’s, we usu-ally mark the placental outlines on the abdominal skinprior to skin preparation and draping, using a surigcalskin marker fiber-tip pen.

Intraoperative management

Cystoscopy

A preoperative cystoscopy is performed in all our caseswith placenta previa or suspected bladder invasion.Complete penetration or excrescences through thebladder mucosa are rare, but venous congestion andareas of hypervascularity are commonly visible in caseswith placenta increta–percreta (Figure 10).

Ureteric stenting

The place of ureteric stenting in the management ofthe MAP remains in question68. The potential benefitsinclude earlier intraoperative diagnosis of uretericinjury and more rapid and easier identification ofinjured ureters even in the presence of profuse bleed-ing68. However, some surgeons argue that the process

of stenting abolishes the elasticity of the ureters andmakes them more liable to injury than when normalrecoil and peristaltic activity is present69. In addition,stenting could possibly kink or displace (and therebyrelocate) the ureters, increasing their risk of damageduring surgery69.

Perhaps of greater relevance to the more invasivegrades of MAP, it has been argued that even if uretericstenting does not prevent ureteric injuries, it doesnot permit such injury to go unrecognized at surgery.This is important, because non-recognition of uretericinjury leads to serious complications. That being said,ureteric stenting is not without risk of complicationsitself67–69, including urinary tract infection, reflexanuria secondary to ureterovesical junction edema,renocortical vasoconstriction following catheter stim-ulation, and even the rare ureterovenous fistula70. In arecent study, it was determined that although uretericstenting did not seem to lead to a reduction in uretericinjury, its use was associated with a reduction in earlypostoperative morbidity71.

Direct visualization of the ureters during surgery isthe only proven preventive measure against injury73.Prophylactic ureteric stenting does not eliminate

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Checklist for operative equipment and supplies

1. Cell salvage machine

2. Central arterial line

3. High pressure suction pumps

4. Wide bore intravenous access x 2

5. High volume intravascular infusion pumps

6. 4 units of crossmatched packed red blood cells(2 units in the delivery suite fridge for immediate use)

7. Clotting factors and fresh frozen plasma

8. Body warmers and warming blankets, Bair-Hugger®

and space blankets 9. Intraoperative calf-compression devices – Flowtron®

boots 10. Instruments for cystoscopy, ureteric stenting, bowel

and bladder resection and a vascular surgery set

Details

Figure 9 Morbidly adherent placenta (MAP) preoperativechecklist: equipment and supplies

Figure 10 Cystoscopic image showing dilated venous channelswith a placenta increta

ureteric injuries and can therefore not replace directvisualization of the ureters and meticulous surgicaltechnique to avoid complications72–74.

In summary, although ureteric stenting cannoteliminate ureteric injuries, it may be advisable wherean increased risk of injury is present69. The greatestblood loss occurs during dissection of the bladderfrom the lower uterine segment, and the presence ofureteric stents allows more rapid, continuous localiza-tion of the ureters, a process that may reduce operativetime and blood loss as well as the likelihood of uretericinjury73.

In our unit, we insert ureteric catheters in cases with blad-der base involvement, posteroinferior bladder wall infiltrationor parametrial extension because of the likelihood that moreextensive dissection would be required, thereby increasing therisk of ureteric damage (Figure 11).

Operative delivery of the infant

The fetal presentation and position are checked preop-eratively by ultrasound in anticipation of any manipu-lations that may be required to effect delivery. Aclassical cesarean or transfundal uterine incision75 ismade away from the upper placental margin that hasbeen marked preoperatively, to effect delivery of theinfant without impinging on the placenta (an image offundal delivery is found in Chapter 1). The umbilicalcord is then ligated, transected and trimmed close to itsplacental insertion. Where antenatal ultrasound andMRI scans have shown morbid adherence and there isintraoperative evidence of the same, no attempt ismade at placental removal. Forceful or delayed attempts atplacental removal are not to be made because of the risk ofsevere life-threatening hemorrhage, therefore uterotonicsare given at this stage, and the uterine incision isclosed.

Selective arterial embolization (Figure 12) or surgi-cal ligation is then performed to reduce the utero-placental blood supply. In most of our cases, we clampboth internal iliac arteries temporarily until the hyster-ectomy is completed, only surgically ligating thesewhere there is or has been significant bleeding. In caseswith moderate bladder involvement, we perform awide anterior uterine wall dissection next, reflectingthe bladder to expose the lower segment and cervix,and the hysterectomy then follows. The bipolardiathermy forceps and hemostatic clips such asthe titanium ligaclips (Ethicon Inc, Sommerville NJ,USA), instruments not routinely used in gynecologicalsurgery, are useful in this endeavor. In other, moresevere cases, a bladder wedge resection or partialcystectomy may be required. Complete vault closureor re-peritonealization of the vault is not advisable insuch cases, because leaving the cuff open permits anypostoperative bleeding to become apparent. In othercircumstances, faced with brisk ongoing hemorrhage,it is a good idea to perform a subtotal hysterectomyfirst to arrest the bleeding, as both the uterine andovarian arteries are usually ligated with the firstpedicles taken65.

An alternative one-step, conservative surgicalmethod has also been proposed as treatment forplacenta percreta45. The report emanates from a unitwith vastly experienced surgeons who have extensiveexperience with this method which involves extensivedissection and the use of surgical mesh. Although itmay hold a place in the management of the moreseverely invasive placenta percreta, it may not be asappropriate in treating lesser degrees of the condition,particularly in the hands of surgeons who are

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The Management of Placenta Accreta at Queen’s Hospital, Romford, UK

Figure 11 Intraoperative image showing placenta increta

Figure 12 Selective endovascular arterial embolization

unfamiliar with the extensive dissection techniquesrequired for its completion45.

In our experience, during the immediate postnatalperiod a substantial degree of the florid vascularizationand engorgement subsides; therefore, in cases withsevere bladder or extensive parametrial invasion, weretain the placenta and an interval hysterectomy isarranged. Where vascular clamps or embolizationcatheters have been applied, these are removed afterthe hysterectomy is complete and hemostasis isensured.

Tissue reconstruction is commenced once this hasbeen achieved. The suture lines created between thebladder and posterior vaginal wall are then coveredwith an interpositional peritoneal or omental flap ifthe latter is easily accessible. A U-shaped flap ofperitoneum covering the bladder dome is inverted andtacked down onto the vaginal suture line to providesupport as previously described by a member of ourteam77. A wide bore Robinson’s or corrugated Yatesdrain is left behind, with mass closure of the abdomenusing loop nylon sutures followed by skin closure withsutures or staples.

Various means are available for measuring operativeand immediate postpartum blood loss to ensure thatblood replacement is adequate38. At Queen’s, all surgi-cal swabs and sponges are weighed to quantify theblood loss at surgery. We commence blood replace-ment intraoperatively with the use of the cell salvagemachine as guided by the estimation, the patient’s vitalsigns and central venous pressure monitoring.

Postpartum management

After surgery in elective cases, the woman is trans-ferred to either the delivery suite or the obstetric highdependency unit for close postoperative monitoring,further stabilization and care. In the acutely ill orwhere maternal condition has deteriorated duringsurgery, transfer to the intensive care unit is arrangedfor close monitoring, blood and fluid replacement,and correction of any acidosis, hypothermia, orcoagulopathy.

Because postpartum hemorrhage is the commonestcomplication of morbid placental adherence, closeobservation of blood loss, abdominal drains and inten-sive monitoring of fluid input and output is crucial.Central venous pressure line monitoring helps reducethe well known underestimation of blood loss at sur-gery. Stable vital signs and a good hourly urine outputare favorable prognostic signs.

Postoperative thromboprophylaxis

There is an increased risk of venous thromboembolismbecause of the prolonged operating time, heavy bloodloss, the extensive pelvic dissection and tissue manipu-lation, and reduced mobility postoperatively. Prophy-lactic heparin should therefore be given39. We usepneumatic limb compression devices (Flowtron®

boots) intraoperatively and administer prophylactic

low molecular weight heparins postoperatively for6 weeks.

SUMMARY AND CONCLUSIONS

We have discussed the contemporary diagnosis andmanagement of MAPs against the background of the5-year experience in our obstetric unit. Traditionally,management of MAP centered around hysterec-tomy71, but recently the emphasis has changed to favorother, minimally invasive and fertility preservingoptions41–46,52,79. Although conservative managementstrategies carry a significant risk of maternal morbidityand mortality, they remain viable options that can besafely exercised.

Proper management should be based on accurateearly diagnosis with appropriate perioperative multi-disciplinary planning to anticipate and avoid massiveobstetric hemorrhage at delivery. Previously noveltreatment options and appliances such as the Bakritamponade balloon and radiological transcatheter arte-rial embolization have rapidly acquired key manage-ment roles in the management of MAP.

Women at risk should be delivered at centers withappropriate expertise and resources for managing thiscondition. The evidence base for the management ofMAPs is not always clear, leaving room for debateover some of the strategies recommended. Furtherclinical evidence and reports are needed to guideappropriate service planning, provide accurate infor-mation to support the counseling of women about theassociated risks, and develop management guidelinesto enhance patient safety.

ACKNOWLEDGMENTS

We would like to acknowledge the tremendous con-tributions of all those involved in the multidisciplinarymanagement of MAP at our institution without whomnone of this would have been possible. This includesall the sonographers, blood transfusion specialist prac-titioners, members of the midwifery teams, deliverysuite, operating theater staff, the interventional radiol-ogy team and staff from the hospital portering service.

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