nAmerican Journal of Obstetrics and Gynecology (2005) 193, 10459Department of Obstetrics and Gynecology, American University of Beirut Medical Center, Beirut, Lebanon

Received for publication March 1, 2005; revised May 18, 2005; accepted June 7, 2005

KEY WORDSPlacenta

PreviaAccretaComplications

Risks

Objective: The purpose of this study was to identify risk factors and complications of placentaprevia-accreta (PA).Study design: Patients with placenta previa (n = 347) delivered over 20 years were reviewed,divided into PA (cases, n = 22) and no accreta (controls, n = 325), and compared.Results: Cases were older with a higher incidence of smoking and previous cesarean delivery(CS). Grandmultiparity, recurrent abortions, anterior/central placentae, and low socioeconomic

status were similar. PA incidence increased with the number of previous CS: 1.9%, 15.6%, 23.5%,29.4%, 33.3%, and 50.0% after 0, 1, 2, 3, 4, and 5 previous CS, respectively. Hypertensivedisorders (odds ratio [OR] 13.9, 95%CI 2.1-91.2], P= .006), smoking (OR 3.4, 95%CI 1.1-10.2,

P= .031) and previous CS (OR 7.9, 95%CI 1.7-37.4, P= .009) were selected by the stepwiselogistic regression analysis as predictors of PA. Cases had a longer hospital stay, a higherestimated blood loss, and need for transfusion. Cesarean hysterectomy and hypogastric arteryligation were only performed in PA cases. The 2 groups had a similar delivery gestational age and

neonatal outcome.Conclusion: Hypertensive disorders, smoking, and previous cesarean are risk factors for accretain placenta previa patients. Placenta previa-accreta is associated with higher maternal morbidity,

but similar neonatal outcome compared with patients with an isolated placenta previa. 2005 Mosby, Inc. All rights reserved.

The incidence of placenta previa which requires ab-dominal delivery is 0.33% of all deliveries.1 Risk factorsfor placenta previa include previous uterine scar, smok-ing, maternal age over 35 years, grandmultiparity, recur-rent abortions, low socioeconomic status, infertilitytreatment, and male gender. In addition to hemorrhagic

Placenta accreta occurs when there is a defect of thedecidua basalis, resulting in abnormally invasive implan-tation of the placenta.6 Risk factors for accreta includeplacenta previa, maternal age over 35 years, grandmulti-parity, previous curettage, previous myomectomy, previ-ous uterine surgery, submucous myoma, AshermansPlacenta previa-accreta: Risk

Ihab M. Usta, MD, Elie M. Hobeika, MD, AGaby E. Gabriel, MD, Anwar H. Nassar, MDcomplications, placenta previa is associatedwith abruptioplacentae, congenital malformations, abnormal presen-tations, and preterm delivery.2-5

Presented at the Twenty-Fifth Annual Meeting of the Society for

Maternal Fetal Medicine, February 7-12, 2005, Reno, Nev.

Reprints not available from the authors.

0002-9378/$ - see front matter 2005 Mosby, Inc. All rights reserved.doi:10.1016/j.ajog.2005.06.037factors and complications

toine A. Abu Musa, MD,

www.ajog.orgsyndrome,6-8 a short caesarean-to-conception interval,9

and a female fetus.10 Placenta accreta is associated with7% mortality rate, as well as intraoperative and postop-erative morbidity caused by massive blood transfusions,infection, and adjacent organ damage.6

The rate of placenta accreta in previa cases variesbetween 1.18% and 9.3%.3,11 On the other hand, 10%

of accreta cases have anterior previa.8 Some risk factorsand complications in patients with placenta accretamight be attributed to the coexistence of the 2 entities.We conducted our study to identify risk factors andcomplications of placenta accreta in the presence ofplacenta previa.

Material and methods

Our computer database was used to retrieve all casesadmitted with the diagnosis of placenta previa over 20years (1983-2003). Charts were reviewed for maternaldemographics, including age, parity, gestational age,previous cesarean delivery (CS), placental location, socialstatus, and history of smoking. Data onmode of delivery,estimated blood loss, presence of placenta accreta, pla-cental pathology, bleeding complications, proceduresneeded to control bleeding, and transfusions were docu-mented. Neonatal charts were reviewed for birth weights,Apgar scores at 1 and 5 minutes, intensive care nurseryadmission, respiratory distress, need for mechanical ven-tilation, intraventricular hemorrhage, necrotizing enter-ocolitis, suspected or conrmed sepsis, periventricularleukomalacia, nursery stay, and perinatal mortality.

Patients were divided into those with placenta previa-accreta (PA) (cases) and those without placenta accreta(controls). The 2 groups were compared for maternaldemographics, intrapartum and postpartum complica-tions, and neonatal outcome. Placenta accreta wasdened according to clinical or histologic criteria asfollows: 1) manual removal of the placenta partially ortotally impossible, and no cleavage plane between partor all of the placenta and the uterus; 2) heavy bleed-ing from the implantation site after forced placentalremoval or piecemeal removal of the placenta; or 3)histologic conrmation of placenta accreta.12 Advancedmaternal age (AMA) was dened as age R35 years andgrandmultiparity as parity R5.

Discrete variables were compared with the use of thechi-square test or 2-tailed Fisher exact test if the expectedcell frequencies were small. Continuous variables werecompared by the Student t test. A P value ! .05was considered statistically signicant. Stepwise logisticregression analysis was used to identify risk factors forprevia-accreta. Independent variables included in themodel were: AMA, grandmultiparity, recurrent abor-tions, smoking, anterior or central placental location,hypertensive disorders, and previous cesarean delivery(0, 1, or R2).

Results

A total of 371 patients admitted with the diagnosis ofplacenta previa were reviewed. Apart from the delivery

1046admission, 27.0% were admitted once, 20.8% twice,3.8% 3 times, and .3% 4 times for bleeding, rupturedmembranes, or preterm labor. The mean predeliverystay was 4.93 G 5.16 days (range 1-32) and the deliverystay was 5.90 G 7.2 days (range 1-92). The previa wascomplete in 24.0%, partial in 12.1%, marginal in 7.5%,and low-lying in 15.4%. In 41.0%, the exact location ofthe previa in relation to the cervix was not specied.Risk factors including smoking, AMA, grandmultipar-ity, recurrent abortions, and low socioeconomic statuswere absent in 23.3% of patients.

After excluding 12 patients delivered in an outsidehospital and 12 delivered at!24 weeks of gestation, 347patients were analyzed for their delivery admission. Theplacenta was PA in 22 (cases) and non-accreta in 325(controls), with a rate of placenta accreta in previapatients of 6.3%.

Table I describes the demographic characteristics ofcases and controls. The incidence of PA was 12.2% insmokers compared with 4.8% in nonsmokers (P= .041)and 1.9% in those with no previous CS versus 21.0% inthe 81 patients with a previously scarred uterus (P !.001). It increased with the number of previous CS at arate of 1.9%, 15.6%, 23.5%, 29.4%, 33.3%, and 50.0%after 0, 1, 2, 3, 4, and 5 previous CS, respectively. Theincidence of PA was signicantly higher in patients withAMA compared with those!35 years (13.6% vs 4.1%,P= .005). Accreta rate was 3.3% in those !25 years,3.4% in those 25 to 29 years, 5.5% in those 30 to 34years, and 13.6% in those with AMA. Although theincidence of PA was higher in grandmultiparas (11.1%vs 5.5%, P= .117), in patients with recurrent abortions(13.0% vs 5.9%, P= .171), in those with low socioeco-nomic status (5.2% vs 7.4%, P= .401), and in thosewith anterior or central placental location (8.9% vs5.1%, P= .258), the dierences did not reach statisticalsignicance.

AMA was not found to be a signicant risk factor forPA when patients were subgrouped according to thepresence (30.3% vs 14.6%, P= .153) or absence (2.1%vs 1.8%, P= 1.000) of a previous scar. Anterior orcentral placental location was found to be a signicantrisk factor in the presence of a previous scar (28.6% vs1.9%, P ! .001), but not in its absence (2.4% vs 6.0%,P= .239).

The variables selected using the stepwise logisticregression analysis as predictors of PA were hyperten-sive disorders (OR 13.9, 95%CI 2.1-91.2, P= .006),smoking (OR 3.4, 95%CI 1.1-10.2, P= .031), andprevious CS (OR 7.9, 95%CI 1.7-37.4, P= .009);more than 1 CS further increased the risk (OR 30.5,95%CI 8.2-113.6, P ! .001).

Table II describes antepartum and peripartum com-plications in cases and controls. The placenta wasremoved piecemeal in 5 (22.7%), suturing of placentalbed was required in 4 (18.2%), hypogastric artery liga-tion in 1 (4.5%), and hysterectomy in 2 (9.1%). Placenta

Usta et al

accreta was conrmed in both hysterectomy specimens.Blood loss was estimated at R3000 mL in 22.7% casescompared with only .3% controls (P ! .0001) andtransfusion with R5 units was needed in 9.1% casesversus 3.1% controls (P= .172). We had no cases ofbladder or bowel invasion and no maternal mortalities.

Table III describes the neonatal outcome in cases andcontrols. The outcome was similar in all respects,including respiratory distress (9.1% and 11.1%), needfor mechanical ventilation (4.5% and 13.2%), intraven-tricular hemorrhage (0% and 3.7%), necrotizing enter-ocolitis (0% and 1.5%), suspected sepsis (13.6% and14.2%), conrmed sepsis (0% and 2.2%), patent ductus(4.5% and 1.5%), periventricular leukomalacia (0% and.6%), and retinopathy of prematurity (4.5% and .3%) incases and controls, respectively.

Comment

The rate of placenta accreta in the literature variesbetween 0.001% and 0.9% of deliveries, a rate thatdepends on the denition adopted for accreta (clinical orhistopathologic diagnosis) and the population studied.8

There has been an almost 10-fold increase in theincidence of accreta in recent years compared withthat reported in the 1950s, probably resulting from theincreased cesarean section rate.6,11

The rate of accreta in our previa cases was 6.3%. Oneof the factors highly associated with PA was previousCS, where the rate of PA increased with the number ofprevious CS. The risk for PA in patients with one CSwas w8-fold higher compared with those with anunscarred uterus and further increased w4-fold with 2or more CS. The same was observed in a recentlypublished abstract from the Maternal Fetal MedicineUnit Cesarean Section Registry, although the rate of

Table I Demographic characteristics

CharacteristicsCases(n = 22)

Controls(n = 325)

Pvalue

Age (y)*y 32.6 G 4.80 30.0 G 5.77 .040R35 (%)* 50.0 21.5 .005

Parityy 3.25 G 2.43 2.54 G 2.51 .199Grandmultiparity (%) 27.3 14.8 .207

Smoking (%)* 40.9 20.0 .041Low socioeconomic

status (%)40.9 50.2 .536

Previous cesarean (%)* 77.3 19.7 ! .001Recurrent abortionsR3 (%)

13.6 6.2 .171

Anterior or centralplacenta (%)

45.5 31.4 .258

* Statistically significant.y Data presented as mean G standard deviation.

Usta et alincrease in the incidence of PA with 1 and 2 CS waslower than previously reported (3.3% and 11.0%,respectively).13 Miller et al11 studied 590 cases of pla-centa previa and found a rate of PA of 4%, 14%, 23%,35%, 50% after 0, 1, 2, 3, and 4 CS, respectively. Theincidence of accreta was higher in other reports reaching4% to 5%, 24%, 60%, and 67% after 0, 1,R3, andR4CS7,14 and even higher, reaching 34.8%, 56%, 75%, and100% after 0, 1, 2, andR2 CS.15 The American Collegeof Obstetrics and Gynecology (ACOG) warns of a rateof accreta of 40% in patients with more than 2 CS andanterior or central placenta previa.6

Table II Antepartum and peripartum events

CharacteristicCases(n = 22)

Controls(n = 325)

Pvalue

Needed antepartumadmission (%)

45.5 52.9 .210

Bleeding as indicationfor delivery (%)

31.8 34.5 .984

Diabetes (%) 4.5 1.5 .327Hypertensive

disorders (%)*13.6 3.1 .042

Vaginal delivery (%)* 0 24.3 .006Abruptio (%) 0 7.7 .387Maternal hospital

stay (days)*y12.8 G 9.0 5.5 G 5.3 ! .001

Estimated bloodloss (ml)*y

2262 G 1261 847 G 420 ! .001

Transfusion (%)* 95.5 25.2 ! .001Excessive bleeding (%)* 100.0 27.1 ! .001

* Statistically significant.y Data presented as mean G standard deviation; excessive

bleeding = postpartum hematocrit !25%, or blood loss O1200 mL,or drop in hematocrit R10 units or needed transfusion.

Table III Neonatal outcome

CharacteristicCases(n = 22)

Controls(n = 325)

Pvalue

Gestational age (wk)* 35.90 G 2.76 36.14 G 3.70 .808Birth weight (g)* 2948 G 642 2753 G 800 .207Preterm delivery!28 weeks (%) 4.5 4.3 1.000!32 weeks (%) 9.1 12.6 1.000!37 weeks (%) 45.5 37.2 .295

Apgar score at1 min*

6.52 G 2.36 6.50 G 2.64 .973

Apgar score at5 min*

8.52 G 2.04 8.13 G 2.42 .471

ICN admission (%) 22.7 36.6 .278Perinatal mortality

(per thousand)45 110 .491

ICN, Intensive care nursery.

* Data presented as mean G standard deviation.

1047

Our study shows an almost stable rate of accreta untilmaternal age exceeds 35 when the incidence of accretarises dramatically. Advanced age and previous uterinescar seem to act synergistically to increase the risk ofPA. AMA was also an important risk factor for PA ina study by Lachman et al.16 Miller et al11 reported anincrease in accreta incidence with age, but the increasewas progressive with a rate of PA of 3.2%, 6.2%,10.2%, and 14.6% for those!25, 25 to 29, 30 to 34, andR35 years, respectively.

The incidence of PA was not signicantly higher ingrandmultiparous women. Zaki et al14 reached similarconclusions where the eect of age and parity was lessdramatic than previous scar. Unlike previous reports,8,11

we did not nd a higher incidence of accreta with ananterior or central placenta; however, the location of theplacenta had an impact only in those with a previouslyscarred uterus. Recurrent abortions were not associatedwith a higher incidence of accreta, although previouscurettage was previously reported as an important riskfactor for PA, in which the incidence of accreta was36%, 58%, and 70% in those with 0, 2, and 3 previouscurettages, respectively.15

Although peripartum complications were higher inPA cases, the rate of antepartum complications, how-ever, was similar, except for hypertensive disorders. It isplausible that hypertensive disorders might be a riskfactor for accreta because of the possible vascular endo-thelial damage in hypertension. On the other hand,placenta accreta might increase the risk for preeclampsiacaused by abnormal trophoblastic invasion. Furtherstudies are needed to test this hypothesis and conrmthis association. The possible overlap between previousCS, maternal age, parity, and hypertensive disorders wasaccounted for using stepwise logistic regression analysis.CS and hypertensive disorders remained signicantindependent of maternal age.

Identifying risk factors is important because sono-graphic, Doppler, and magnetic resonance imagingdiagnosis of placenta accreta is now possible,17-19 andin settings where these diagnostic capabilities are avail-able, clinical risk factors may be used as screeningcriteria for placenta accreta. In emergency situations orin settings in which ultrasonographic diagnosis is notavailable, awareness of clinical risk factors can aid incareful preoperative preparation and in counsellingwomen with placenta previa regarding the likelihoodof encountering placenta accreta with its attendantmorbidity as recommended by ACOG and Royal Col-lege of Obstetricians and Gynaecologists (RCOG).6,20

Compared with previa patients, cases with PA had ahigher incidence of bleeding complications and a longermaternal hospital stay. Our complication rate washigher than previously reported for cases of placentaaccreta in general, where only 21% required transfusionand 3.5% ended in hysterectomy.8 Both patients that

1048required hysterectomy had placenta accreta (9.1%).Patients with placenta previa and scarred uterus arereported to have a 16% chance of undergoing hysterec-tomy for accreta compared with 3.6% risk for hyster-ectomy in cases of placenta previa and an unscarreduterus.1 The rate of peripartum hysterectomy is 1.0 to1.4 per thousand of deliveries,7,15,21,22 and placentaaccreta is reported as the leading15,22 or the secondmost common indication for peripartum hysterectomy,7

constituting 23.8% to 64% of these cases.21 In one of thereports, PA constituted 8.5% of these cases.15

Although a few reports have been published docu-menting dierences in risk factors between patients withprevia alone compared with patients with PA,11,14 littlehas been mentioned about dierences in perinatal out-come. Earlier reports have shown that placenta accretawas associated with higher rates of small-for-gestationalage, preterm delivery, and perinatal mortality comparedwith normal pregnancies. Similar to Miller et al,11 ourstudy shows a similar gestational age at delivery, com-parable birth weight, and no dierence in perinatalmorbidity and mortality between placenta previa andPA patients. Our perinatal mortality rates were rela-tively high in both cases and controls. This could bepartially attributed to including older cases dating backto 1983 before the advances in neonatal care. In fact,this is one of the limitations of the present study thatcould have potentially skewed our results because theprevalence of risk factors like previous CS and AMAmight have changed over time.

In conclusion, hypertensive disorders, smoking, andprevious cesarean are risk factors for placenta accreta inprevia patients. Placenta previa-accreta is associatedwith a higher maternal morbidity compared withisolated previa without signicant dierences in theneonatal outcome.

Acknowledgments

We would like to acknowledge Dr Hala Tamim from theDepartment of Epidemiology and Population Health atthe American University of Beirut for her assistance inthe statistical analysis.

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Placenta previa-accreta: Risk factors and complicationsMaterial and methodsResultsCommentAcknowledgementsReferences