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O B S T E T R I C S

Screening for placenta accreta at 11-14 weeks of gestationJulien J. Stirnemann, MD; Eve Mousty, MD; Gihad Chalouhi, MD; Laurent J. Salomon, MD, PhD;

Jean-Pierre Bernard, MD; Yves Ville, MD

OBJECTIVE: We sought to describe the potential value of 11-14 weeks

screening for placenta accreta (PA).

STUDY DESIGN: Patients with a history of lower segment cesarean

section were prospectively included between 11-136 weeks over a

1.5-year period. The first 258 were offered standard screening

whereas the following 105 underwent screening for PA. Women were

considered high-risk when the trophoblast overlapped the scar visual-

ized by transvaginal ultrasound and low-risk otherwise.

RESULTS: The group screened for PA did not differ from the non-

screened group for demographic characteristics. In all, 6 of 105 (5.8%)

women were considered high-risk. In the nonscreened group, 1 case of

PA was discovered during an elective repeat cesarean. In the screened

population, 1 case of PA occurred in a high-risk patient allowing a con-

servative planned management at 35 weeks.

CONCLUSION: At 11-14 weeks, ultrasound may help risk stratification

for PA with a specific follow-up. Early recognition of patients at risk

might improve the perinatal outcome of PA.

Key words: cesarean, first trimester, placenta accreta, screening,

ultrasound

Cite this article as: Stirnemann JJ, Mousty E, Chalouhi G, et al. Screening for placenta accreta at 11-14 weeks of gestation. Am J Obstet Gynecol

2011;205:547.e1-6.

P lacenta accreta (PA) is a life-threat-ening obstetrical condition that oc-curs when a defect of the decidua basalis

enables the direct apposition of chori-

onic villi to the myometrium. As a result,

at least part of the placenta cannot sepa-

rate after delivery and this may lead to

severe obstetric hemorrhage.1-5 It has

become the principal indication forpostpartum hysterectomy as well as for

related surgical injuries.6-10 The inci-

dence of PA has increased 4-fold from

199411 through 2002,12 following the in-

crease in cesarean delivery rates over the

same period of time. Most PA present as

placenta previa in the third trimester

with an incidence of 9.3% in this group

compared with 0.005% when the pla-

centa is normally inserted.11 Among

women with placenta previa, maternal

age35 years and previous cesarean de-

livery are independent risk factors, with

an incidence of 2% for women aged35

years and no cesarean section up to 38%

in women aged35 years and2 previ-ous cesarean sections.11

It is important to diagnose PA prior to

delivery, to allow for optimal concerted

management planning and prevention

of severe maternal morbidity and mor-

tality.13-17 The diagnosis of PA by ultra-

sound and magnetic resonance imaging

(MRI) in the second and third trimester

of pregnancy remains largely speculative,

even in high prevalence cohorts,18-21 and

most cases are only diagnosed at the time

of delivery in cases with prepartum or

postpartum hemorrhage.13-16 The timing

of the defective trophoblast implantation

leading to PA suggests that this condition

couldbeidentifiedduringthe11-14weeks

ultrasound.

Signs of PA have been recognized as

early as the first trimester in several case

reports.22-26 However, these findings

have never been implemented in a pro-

spective early screening strategy. The

main aim of our study was to describethe potential use of routine 11-14 weeks

scan27 for screening for PA in women

with a history of delivery by lower seg-

ment cesarean section (LSCS).

MATERIALS AND METHODS

The screening procedure for PA was de-

fined inpatients with a history of LSCS as

follows: a transvaginal midsagittal planewas defined, including the cervical canal,the bladder, and the lower part of the

gestational sac.28 Both the uterine scar

and the location of the trophoblast were

recognized and located. The relationship

between the uterine scar and the tropho-

blast thus defined the high-risk group. A

patient was considered high-risk when

the scar was exposed within the uterine

cavity above the lowest part of the gesta-

tional sac, which encompasses the cervix

and part of the inferior segment togetherwith a covering low-lying placenta (Fig-

ure 1).28 A patient was considered low-

risk eitherwhen the uterine scar was pro-

tected within the cervicoisthmic canal

(Figure 2, A) or when the trophoblast

was not covering the internal os (Figure

2, B).28

The population considered for this

study comprises all consecutive cases of

patients with a history of lower segment

uterine scar over a 1.5-year period (Sep-

tember 2008 through March 2010) at-tending our unit for first-trimester

From the Department of Obstetrics and

Maternal-Fetal Medicine, GHU Necker

Enfants Malades, Universit Paris Descartes,Paris, France.

Received Feb. 9, 2011; revised May 29, 2011;accepted July 13, 2011.

This study was supported by the SocitFranaise pour lAmlioration des PratiquesEchographiques in setting teaching sessions.

The authors report no conflict of interest.

Reprints: Yves Ville, MD, Maternit, HpitalNeckerEnfants Malades, 149 rue de Svres,75015 Paris, France. [email protected].

0002-9378/$36.00 2011 Mosby, Inc. All rights reserved.

doi: 10.1016/j.ajog.2011.07.021

Research www.AJOG.org

DECEMBER 2011 American Journal of Obstetrics &Gynecology 547.e1
mailto:[email protected]:[email protected]:[email protected]

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screening at 11-136 weeks as defined

by a crown-rump length between 45-84

mm. During a first period of time, pa-

tients were not specifically screened for

placenta and scar location. In a second

period, patients were screened for PA by

transvaginal ultrasound.All ultrasounds were performed usinga General Electrics Voluson E8 or 730

Expert (GEMedical SystemEurope, Buc,

France) with a 3.5- to 5-MHz or 6- to

8-MHz transvaginal transducer.

Demographic data as well as obstetri-

cal and perinatal management and out-

come were prospectively recorded in our

electronic database (Astraia, Munich,

Germany). Patients considered high-risk

were followed up prospectively with se-

rial ultrasound focusing on ultrasoundsigns of placental invasion in our unit up

until delivery.

The statistical analysis was conducted

using R (www.r-project.org). Quantita-

tive variables are summarized by the me-

dian and interquartile range (25th-75th

centile) and qualitative variables are de-

scribed by N (%). Comparisons of de-

mographic characteristics between the

screened and nonscreened populations

were performed using Mann-WhitneyU

tests for quantitative variables and Fisherexact tests for qualitative variables.Since transvaginal ultrasound is of-

fered routinely for first-trimester screen-

ing in our practice, this study did not re-

quire an institutional review board;

however, written informed consent was

obtained from all women.

RESULTS

Over the study period, 363womenwith a

history of LSCS attended our unit forfirst-trimester screening at 11-136

weeks gestation. Among these, the first

258women were screened only for aneu-

ploidy and fetal defects whereas the fol-

lowing 105 were also prospectively

screened for PA. No significant differ-

ences in demographic characteristics

were found between thescreenedand the

nonscreened populations (Table 1). In

particular, considering risk factors for

PA, maternal age (P .12), parity (P

.46), number of scars (P

.28), andratesof emergency cesarean operations (P

FIGURE 1

Exposed scar with overlapping trophoblast (T) defining high-risk group

Arrows uterine scar.

B, bladder; C, cervix; GS, gestational sac.

Stirnemann. Screeningfor placenta accreta at 11-14weeks. Am J Obstet Gynecol 2011.

FIGURE 2

Protected and exposed scars

A, Protected scar with trophoblast (T) overlapping internal os. B, Exposed scar with nonoverlapping T.Arrows uterine scar.

B, bladder; C, cervix; GS, gestational sac.


Research Obstetrics www.AJOG.org

547.e2 American Journal of Obstetrics &Gynecology DECEMBER 2011
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.06) were similar. The overall rate of loss

to follow-up was 38/363 (10.5%) and

was similar in both groups(9/105 [8.6%]

and 29/258 [11.2%], P .57). The deliv-

ery mode was unknown in 5 cases.

Obstetrical and perinatal manage-

ment of the study population is summa-rized in Figure 3. Two patients under-went termination of pregnancy and 3

miscarried 24 weeks gestation. These

patients together with 3 cases of intra-

uterine fetal demise delivered vaginally.

All live-born pregnancies with at least 2

uterine scars delivered by elective cesar-

ean whereas patients with only 1 scar

attempted vaginal birth in 162/262

(61.8%) with a 105/262 (64.8%) success

rate.

Perinatal complications related to priorcesarean included 2 cases (0.6%) of PA, 16

cases (5%) of severe postpartum hemor-

rhage requiring sulprostone or surgery, 2

cases (0.6%)of placentaprevia, and2 cases

(0.6%) of complete uterine rupture. The

occurrenceofPAinthestudypopulationis

summarized in Figure 4 with respect to

screening results.

Within the nonscreened population, 1

case of placenta percreta was discovered

during elective cesarean at 395 weeks

in a 31-year-old, 4-parous patient with ahistory of 2 cesareans. This patient hadan uneventful follow-up until delivery.

Upon opening of the peritoneum, pla-

cental bulging through the anterior uter-

ine wall required a fundal incision. A con-

servative management was performed

leavingtheplacentaand theuterus. Embo-

lizationof uterineandinternaliliacarteries

was subsequently performed. Follow-up

was uneventful apart from episodic bleed-

ing without signs of infection, with MRI

examinations showingprogressive involu-tion of the placenta at 8 months after

cesarean.

Withinthe screened population, 1 scar

was not visualized, 6 of 104 (5.8%) pa-

tients were considered high-risk based

upon a trophoblast overlapping an ex-

posed scar, and 98 of 104 were consid-

ered low-risk.One case of PA wasdiscov-

ered in the sixth high-risk patient. This

patient had been followed-up by serial

ultrasound at 161,181,221,251,

and 29

1 weeks confirming signs of PAboth on ultrasound and MRI with a low-

lying anterior placenta. Elective cesarean

section was performed at 35 weeks under

epidural anesthesia after a course of be-

tamethasone given for fetal lung matu-

rity enhancement. The inferior segment

was richly vascularized. Hysterotomywas performed through a fundal vertical

incision.No attempt was made to extract

the placenta. Uterine and internal iliac

arteries embolization was then per-

formed systematically. Blood loss was

300 mL and the postpartum period was

uneventful. The placenta was still intra-uterine at 3 months when she developed

TABLE 1

Comparison of demographic characteristics betweenscreened and nonscreened populations

Characteristic

OverallWithout 11-14 wkscreening

With 11-14 wkscreening

Pvaluen 363 n 258 n 105

Age, y .12..............................................................................................................................................................................................................................................

Median (IQR) 35 (3138) 35 (3239) 34 (3038).....................................................................................................................................................................................................................................

Missing 0..............................................................................................................................................................................................................................................

Parity .46.....................................................................................................................................................................................................................................

1 212 (58.4%) 157 (60.9%) 52 (55.9%).....................................................................................................................................................................................................................................

1 139 (38.3%) 101 (39.1%) 41 (44.1%).....................................................................................................................................................................................................................................

Missing 12 (3.3%)..............................................................................................................................................................................................................................................

No. of scars .28.....................................................................................................................................................................................................................................

1 305 (84.0%) 221 (85.7%) 84 (80%).....................................................................................................................................................................................................................................

2 54 (14.9%) 34 (13.2%) 20 (19%).....................................................................................................................................................................................................................................3 4 (1.1%) 3 (1.1%) 1 (1%).....................................................................................................................................................................................................................................

Missing 0..............................................................................................................................................................................................................................................

Interval since last delivery, mo .14.....................................................................................................................................................................................................................................

Median (IQR) 28 (1249) 26.5 (11.745.5) 32 (1454).....................................................................................................................................................................................................................................

Missing 137 (37.7%)..............................................................................................................................................................................................................................................

History of vaginal birth .36.....................................................................................................................................................................................................................................

Yes 64 (17.6%) 42 (17.4%) 22 (21.8%).....................................................................................................................................................................................................................................

No 279 (76.9%) 200 (82.6%) 79 (78.2%).....................................................................................................................................................................................................................................

Missing 20 (5.5%)..............................................................................................................................................................................................................................................

VBAC .16.....................................................................................................................................................................................................................................

Yes 33 (9.1%) 27 (11.3%) 6 (5.8%).....................................................................................................................................................................................................................................

No 309 (85.1%) 212 (88.7%) 97 (94.2%).....................................................................................................................................................................................................................................

Missing 21 (5.8%)..............................................................................................................................................................................................................................................

Emergency cesarean .06.....................................................................................................................................................................................................................................

Yes 119 (32.8%) 77 (29.8%) 42 (40%).....................................................................................................................................................................................................................................

No 244 (67.2%) 181 (70.2%) 63 (60%).....................................................................................................................................................................................................................................

Missing 0..............................................................................................................................................................................................................................................

Postpartum pyrexia .38.....................................................................................................................................................................................................................................

Yes 15 (4.1%) 9 (3.5%) 6 (5.7%).....................................................................................................................................................................................................................................No 348 (95.9%) 249 (96.5%) 99 (94.3%).....................................................................................................................................................................................................................................

Missing 0..............................................................................................................................................................................................................................................

IQR, interquartile range; VBAC, vaginal birth after cesarean.


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endometritis and hysterectomy was eas-

ily performed without technical prob-

lems. She was discharged home after 54

days. Pathology examination confirmed

placenta increta. The 5 other patients

considered high-risk based upon 11-14

weeksultrasound hadan uneventful fol-low-up (Table 2) and delivered vaginally(n 2) or by cesarean (n 3) without

complications at between 38-40 weeks

gestation.

COMMENT

PA is a life-threatening obstetrical emer-

gency. Its incidence has risen in parallel

with that of cesarean deliveries and it re-

mains a major cause of maternal mortal-

ity and morbidity as the principal indi-cation for postpartum hysterectomy

with high blood loss, intensive care unit

admission, and intraoperative injury to

the bladder or bowel.13,15,16

Efforts have been made to refine the

ultrasound diagnosis of PA in the second

and third trimester of pregnancy, con-

sisting in the presence of placental lacu-

nae (irregularly shaped vascular spaces

with turbulent blood flow at the color

Doppler), loss of retroplacental clear

space, thinning of the myometriumoverlying the placenta and interruptionof the bladder line with protrusion of the

placenta into the bladder, or evidence of

hypervascularization by Doppler.21,29-31

The performance of ultrasound has been

studied in very high-risk populations,

with a prevalence of PA ranging from

9-44%. In these studies the sensitivity

of ultrasound, with 1 contemporary

signs, varies from 77-93% and the posi-

tive predictive value from 65-93%.18-21

Although MRI may help refine the diag-nosis following ultrasonography,32,33 its

overall sensitivity remains unclear.19,29

However, most cases of PA remain undi-

agnosed until the time of delivery.13,15,16

PA, however, is likely to develop at the

time of the trophoblast invasion in the

first trimester.34,35 The study of the tro-

phoblasts location in the first trimester

is feasible as part of the routine 11-136

weeks scan. Mustaf et al36 in 2002 have

well established the probability of pla-

centa previa at termin relationto the dis-tance/overlap of the lower placental edge

FIGURE 3

Obstetric management of delivery in study population

IUFD, intrauterine fetal demise; LSCS, lower segment cesarean section; LTFU, lost to follow-up; TOP, termination of pregnancy.


FIGURE 4Flowchart of study population with respect toscreening and occurrence of placenta accreta

LSCS, lower segment cesarean section; LTFU, lost to follow-up.




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with respect to the internal cervical os.

The cesarean scar has been studied and

describedin nonpregnant women as part

of the investigation of the relationship

between scar defects and postmenstrual

spotting, dysmenorrhea, and pelvic

pain.

37-40

The sonographic diagnosis in the firsttrimester has been reported in a few

cases22-25 mainly as a low gestational sac

in early first trimester, suggesting a direct

implantation of the trophoblast over the

scar.26 However, these cases are difficult

to differentiate from ectopic pregnancies

developing in the LSCS scar. These cases

of PA detected in early pregnancy all

showed very specific sonographic fea-

tures. These findings, however, are un-

likely to be fit for 11-14 weeks screeningpolicy, since their prevalence in PA as

well as in normal pregnancies has not

been formally studied. We believe these

ultrasound findings should be used in

second-line diagnostic scans in screen-

positive patients.

Ultrasound examination is now rou-

tinely offered to all pregnant women at

11-14 weeks of gestation in many devel-

oped countries.41 Todate,the aim ofthis

examination is mainly to confirm viabil-

ity and gestational age, diagnose and de-termine chorionicity of multiple preg-nancies, as well as screening for fetal

aneuploidy and for some severe malfor-

mations. Promising attempts at predict-

ing severe obstetrical conditions devel-

oping in the second or third trimester

such as preeclampsia by ultrasound and

Doppler examination at 12 weeks are

promising.42,43 We believe that screen-

ing for PA in a high-risk group with pre-

vious cesarean section is justified by the

severity of this condition at the time ofdelivery andby thefeasibility of both scar

and placental examination at 11-14

weeks.28 Early recognition of PA is likely

to be associated with lesser maternal

morbidity.15,16 Elective cesarean section

with a conservative approach of the pla-

centa left in place has shown to improve

the prognosis for the mother.14 In our

population, a case of placenta percreta

went to delivery undiagnosed in thenon-

screened group, whereas early recogni-

tion of PA in the high-risk group allowedfor planning optimal management. This

suggests that the rationale for 11-14

weeks screening is to help plan further

investigations and follow-up thus avoid-

ing unanticipated peripartum discover-

ies of PA as well as to reassure patients

otherwise at risk based upon demo-

graphic characteristics. Nonetheless, it islikely that a trophoblast overlapping thescar is notthe only factorthat determines

the occurrence of PA. Indeed, as shown

by Miller et al,11 PA may develop at a

distance from the scar at a rate of 3.7%

and 9.1% for patients 35 years and

35 years with 1 previous cesarean sec-

tion. Therefore, although 11-14 weeks

screening is likely to identify most cases

it is anticipated that it will fail in identi-

fying all cases.

We propose that systematic evaluationof the uterine scar and placental location

be tested in a large prospective study at

the time of the 11-14 weeks ultrasound

examination in women with a uterine

scar. Our data suggest that 5.8% of

women with1 previous LSCS could be

considered at high risk of PA with scars

covered by the trophoblast insertion

at 12 weeks. Conversely, scars located

within the cervical canal or yet undevel-

oped isthmus appear to be protected

from this risk even with a low-lying tro-phoblast over the internal os. Account-

ing for maternal age and history could

lead to objective individual risk calcula-

tion for PA as early as 12 weeks and help

refine the care of women, including spe-

cialized imaging investigations such as

an early ultrasound at 16-18 weeks21 or

MRI together with a planned delivery inan appropriate obstetrical unit. f

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Ultrasound follow-up of 6 cases considered high-riskfor placenta accreta by 11-14 weeks screening

CasesGestational age atfollow-up, wk Placental location

1 21

5 Posterior, high............................................................................................................................................................................322 Posterior, high

..............................................................................................................................................................................................................................................

2 176 Anterior, high..............................................................................................................................................................................................................................................

3 183 Posterolateral, low lying............................................................................................................................................................................

222 Posterior, high..............................................................................................................................................................................................................................................

4 160 Posterior, high..............................................................................................................................................................................................................................................

5 284 Posterior, high..............................................................................................................................................................................................................................................

6 161 Anterolateral low-lying............................................................................................................................................................................

181 US signs of placenta accreta............................................................................................................................................................................

221............................................................................................................................................................................

251............................................................................................................................................................................

291..............................................................................................................................................................................................................................................

US, ultrasound.


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