Placenta Accreta Spectrum (PAS) describes abnormal trophoblast invasion into the myometrium, with significant clinical relevance due to life-threatening hemorrhage during delivery. The incidence of PAS has increased from 1 in 30,000 in 1937 to an estimated 0.17% in contemporary populations, primarily driven by rising cesarean section rates. Effective risk assessment and prenatal screening are crucial for managing PAS, as it poses significant challenges in diagnosis and treatment.

1. PAS :
Clinical Classification
Risk Assessment
Dr. Shashwat Jani
M. S. ( Obs – Gyn ), F.I.A.O.G., F.I.C.O.G.
Diploma in Advance Laparoscopy.
Consultant Assistant Professor,
Smt. N.H.L. Municipal Medical College.
S.V.P. Hospital , Ahmedabad.
Mobile : +91 99099 44160.
E-mail : drshashwatjani@gmail.com

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Defined as…
• Placenta accreta spectrum (PAS) is a
general term used to describe abnormal
trophoblast invasion into the myometrium, and
sometimes to or beyond the serosa.
• It is clinically important because the
placenta does not spontaneously separate at
delivery and attempts at manual removal result in
hemorrhage, which can be life-threatening

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Derivation Of Accrete Comes From Latin
AcCrescent = To Adhere Or Become Attached To.

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Placenta accreta is a histopathological term first defined
by the obstetrician frederick c. Irving and the pathologist
arthur t. Hertig from the boston lying-in hospital in 1937.
They defined it as “abnormal adherence of the afterbirth in
whole or in parts to the underlying uterine wall in the partial or
complete absence of decidua”.
CLINICAL OBSTETRICS AND GYNECOLOGY VOLUME 00, NUMBER 00, 000–000
COPYRIGHT © 2018 WOLTERS KLUWER HEALTH, INC.

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Magnitude Of The Problem
• In 1937: 1 in 30 000 deliveries.
• In 1970: 1 in 4000 deliveries in the 1970s
• In 1980: 1 in 2500 deliveries
• In 2010: 3 in 1000 deliveries
• In a 2019 systematic review that included 7001 cases of
PAS among nearly 5.8 million births, the overall pooled
prevalence was 0.17 percent (range 0.01 to 1.1 percent).
The marked increase in PAS, which began in the 1980s
and 1990s and has been observed worldwide, is
attributed to the increasing prevalence of cesarean birth
in recent decades.
Dr Shashwat Jani
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Shah SR, Chudasama T], Patel BS, et al Placenta Accreta spectrum (pas) disorders: A 10-year study at tertiary care
center, Ahmedabad, western India. International Journal of 6. Clinical Obstetrics and Gynaecology.2020; 4:161-6

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Shah SR, Chudasama T], Patel BS, et al Placenta Accreta spectrum (pas) disorders: A 10-year study at tertiary care center, Ahmedabad, western India. International
Journal of 6. Clinical Obstetrics and Gynaecology.2020; 4:161-6

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How…???
• The prevailing hypothesis is that an iatrogenic
defect of the endometrium–myometrial interface leads to a
failure of normal decidualization at the site of a uterine
scar, enabling abnormally deep trophoblast infiltration.
• Disruption of the decidua, for example by a previous
cesarean delivery incision, may result in loss of the inherent
regulation and uncontrolled invasion of extravillous
trophoblast through the entire depth of the myometrium .

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Risk Factors : ( FIGO 2019)
Jauniaux E, Chantraine F, Silver RM, Langhoff-Roos J; FIGO Placenta Accreta Diagnosis and Management Expert Consensus Panel. FIGO consensus guidelines on placenta accreta spectrum
disorders: Epidemiology. Int J Gynecol Obstet. 2018;140:265–273.
Jauniaux E, Jurkovic D. Placenta accreta: Pathogenesis of a 20th century iatrogenic uterine disease. Placenta. 2012;33:244–251.
Luke RK, Sharpe JW, Greene RR. Placenta accreta: The adherent or invasive placenta. Am J Obstet Gynecol. 1966;95:660–668.

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 Predisposing Factors Identified In The 1920s
And 1930s Were Previous Manual Removal Of
Placenta And/Or “Vigorous” Uterine Curettage.
 There Is Now Compelling Epidemiological
Evidence that Accreta Placentation Has
Become Essentially An Iatrogenic Condition,
Secondary To The Modern-era Cesarean
Section Epidemic.

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Biochemical Markers
MSAFP (8 times
higher risk) > 2.5
MoM
Beta hCG (4 times
higher
risk)>2.5 MoM

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PLACENTA PREVIA
• An Important independent risk factor with an
odds ratio of 50-100.
• Accreta incidence has of 1/9 to 1/16 has been
observed among patient with placenta previa at
the time of delivery.
• Maybe due to presence of placenta previa
allowing easier identification of accreta cases but
precluding identification of other independent
risk factors.

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Previous Cesarean Section
• Incidence of PAS disorders increase with the
number of previous cesarean deliveries form about
0.3% in women with one prior cesarean section to
7% for those having more than 5 cesarean
deliveries.
• Incidence of placenta previa and PAS disorders:
– First CS- 3%
– Second CS- 11%
– Third CS- 40%
– Fourth CS- 61%
– Fifth of more- 67%

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 There is now compelling evidence that placenta
accreta spectrum disorders are related to medical
intervention: specifically the caesarean section epidemic.
 More than 90 percent of women presenting with
a placenta accreta have had at least one prior cesarean
delivery, and with the continuous rise in cesarean delivery
rates in most countries around the world, both the prevalence
and incidence of placenta accreta spectrum disorders will
continue to increase.

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• In the absence of placenta previa,
the frequency of a PAS in patients
undergoing cesarean birth was much
lower.
–First (primary) cesarean birth, 0.03 percent
–Second cesarean birth, 0.2 percent
–Third cesarean birth, 0.1 percent
–Fourth or fifth cesarean birth, 0.8 percent
–Sixth or greater cesarean birth, 4.7 percent

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IVF PREGNANCIES
• The accepted hypothesis is differences in the endometrial
environment, or endometrial changes due to drug protocols for IVF.
• The odds ratio of PAS disorders due to IVE-ET is between 3-
14.
• Association of PAS disorders with Cryopreserved Embryo
Transfer or Frozen Embryo Transfer is three times higher than fresh
embryo transfer- one possible mechanism to explain this association
is that the degree of trophoblastic invasion and extent of vascular
remodeling at the time of implantation maybe modulated by serum
E2- level.
• Low E2 level associated with thin endometrium in FET cycle
leading to exuberant trophoblastic growth during a protracted
window of implantation.

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PAS Grading & Classification
 The process of clarifying the reporting data on
placenta accreta in the international literature started
recently with the development of a grading system for the
clinical diagnosis of PAS.
 The classification described was developed from this
grading scheme, and reviewed by members of the FIGO
Placenta Accreta Spectrum Disorders Diagnosis and
Management Expert Consensus Panel.
 For use of the classification, I have summarized the
recommendations of the recent FIGO guidelines for the conservative
and non-conservative surgical management of PAS according to the
grade of accreta invasiveness defined in the present classification.

19. FIGO Classification 2019
General classification of placenta accreta spectrum
Grade 1: Abnormally adherent placenta (placenta adherent or creta)
Grade 2: Abnormally invasive placenta (Increta)
Grade 3: Abnormally invasive placenta (Percreta)

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Grade 1: Abnormally Adherent Placenta
(Placenta Adherent Or Creta)
Clinical Criteria
• At Vaginal Delivery
– No separation with synthetic oxytocin and gentle controlled cord
traction
– Attempts at manual removal of the placenta results in heavy
bleeding from the placenta implantation site requiring mechanical
or surgical procedures.
• If Laparotomy is required (including for cesarean delivery)
– Same as above.
– Macroscopically, the uterus shows no obvious distension over the
placental bed (placental “bulge”), no placental tissue is seen
invading through the surface of the uterus, and there is no or
minimal neovascularity. Dr Shashwat Jani
99099 44160

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Grade 2: Abnormally Invasive Placenta
(Increta)
Clinical Criteria
• At Laparotomy
– Abnormal macroscopic findings over the placental bed:
bluish/purple coloring, distension (placental “bulge”)
– Significant amounts of hypervascularity (dense tangled bed
of vessels or multiple vessels running parallel cranio-caudally in
the uterine serosa)
– No placental tissue seen to be invading through the uterine
serosa.
– Gentle cord traction results in the uterus being pulled inwards
without separation of the placenta (so-called The Dimple Sign)

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Grade 3: Abnormally Invasive Placenta
(Percreta)
Grade 3a : Limited to the uterine serosa:
Clinical Criteria
– At Laparotomy
• Abnormal macroscopic findings on uterine
serosal surface (as above) and placental tissue seen
to be invading through the surface of the uterus
• No invasion into any other organ, including the
posterior wall of the bladder (a clear surgical plane
can be identified between the bladder and uterus)

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Grade 3b: With Urinary Bladder Invasion:
Clinical Criteria
–• At laparotomy
• Placental villi are seen to be invading into the
bladder but no other organs
• Clear surgical plane cannot be identified
between the bladder and uterus
Grade 3: Abnormally Invasive Placenta
(Percreta)

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Grade 3c: With invasion of other pelvic tissue/organs
Clinical Criteria
– At Laparotomy
• Placental villi are seen to be invading into
the broad ligament, vaginal wall, pelvic
sidewall or any other pelvic organ (with or
without invasion of the bladder)
Grade 3: Abnormally Invasive Placenta
(Percreta)

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Prenatal Screening And Diagnosis
• Prenatal screening and diagnosis are important so that the
patient can be counseled about the suspected placental abnormality
and an appropriate site and plan for delivery can be developed.
• Candidates And Procedure For Screening-
– Patients with a placenta previa or a low anterior placenta and
prior uterine surgery should have thorough transabdominal and
transvaginal sonographic evaluation of the interface between the
placenta and myometrium between approximately 18 and 24
weeks of gestation.
– At this gestational age, the prenatal diagnosis of PAS often
can be made or ruled out, although in population-based studies,
prenatal diagnosis was not made in one-half to two-thirds of
cases .

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Risk Assessment
 Clinical risk assessment may be the most
important tool to assess for placenta accreta
spectrum, many studies report very high sensitivity
and specificity for obstetric ultrasonography in the
diagnosis of placenta accreta spectrum.
 For example, a systematic review, including
23 studies and 3,707 pregnancies, noted an average
sensitivity of 90.72% (95% CI, 87.2–93.6) and
specificity of 96.94% (95% CI, 96.3–97.5%

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ACOG
 A reasonable approach is to
perform ultrasound examinations at
approximately 18–20, 28–30, and 32–34 weeks
of gestation in asymptomatic patients.
 This allows for the assessment of previa
resolution, placental location to optimize timing
of delivery, and possible bladder invasion.

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Ultrasound Findings:
In the second and third trimesters, the following
transabdominal and transvaginal sonographic findings have
been associated with PAS; all of the findings need not be
present
Multiple placental lacunae
Disruption of the bladder line
Loss of the clear zone
Myometrial thinning
Abnormal vascularity
Abnormal uterine contour
Exophytic mass

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First-trimester Ultrasound
• PAS should be suspected if ultrasound
examination before 9 weeks reveals
implantation of the gestational sac in the
lower anterior segment of the uterus,
particularly in the niche of the prior cesarean
scar.
• Subsequent placental development in this
area should also raise suspicion for PAS.

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COLOR DOPPLER
• Color Doppler is useful for confirming the
diagnosis of PAS when used in conjunction with the
other ultrasound findings described above.
– Turbulent lacunar blood flow (>15 cm/sec)
– Bridging vessels
– Diffuse or focal intraparenchymal flow
– Hypervascularity of serosa-bladder interface
– Prominent sub-placental venous complex

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3- D Power Doppler Ultrasound
• Three-dimensional ultrasound has been used
successfully for evaluation of PAS.
• Diagnostic Criteria include:
– Irregular intra-placental vascularization with tortuous
confluent vessels crossing placental width.
– Hypervascularity of uterine serosa-bladder wall
interface

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MRI
Uterine bulging into the bladder ("placental/uterine
bulge")
Interruption of the bladder wall
Loss of retroplacental hypointense line on T2W images
Abnormal vascularization of the placental bed
Dark intraplacental bands on T2W imaging ("T2-dark
bands")
Myometrial thinning
Focal exophytic mass

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To Conclude. . .
 PAS is a potentially life-threatening condition.
 Given the increasing rates of cesarean section
worldwide, the incidence of PAS will be likely to
increase further over time.
 Therefore, clinicians should be aware of the
difficulties related with the diagnosis and the
challenges associated with the management of
this condition .

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Scope Of Research…
• It should focus on the collection of data for
prospective studies on the diagnosis and
management of PAS providing correlation
between prenatal imaging, clinical grading of PAS
at the time of delivery, and histopathology.
• This is of paramount importance to provide
the best screening, diagnosis, and management
options to women affected by PAS disorders.

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