Placenta
Abnormal Placentation
Placenta accreta, increta and percreta

Deputy Editor-in-Chief: Jennifer A. Bennett, M.D.
Fabiola Medeiros, M.D.

Minor changes: 11 January 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Placenta[TI] (accreta[TI] OR increta[TI] OR percreta[TI]) review[PT] full text[SB]

Fabiola Medeiros, M.D.
Page views in 2020: 15,942
Page views in 2021 to date: 5,911
Cite this page: Medeiros F. Placenta accreta, increta and percreta. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentaplacentaaccreta.html. Accessed April 16th, 2021.
Definition / general
  • Abnormal placental adherence to the uterine wall
    • Placenta accreta: villi implant on the myometrial surface without intervening decidua
    • Placenta increta: villi extend into the myometrium
    • Placenta percreta: villi penetrate the entire myometrial thickness and through the uterine serosa
Essential features
  • Patients with previous cesarean sections and placenta previa are at high risk for the development of abnormal placental implantation, which includes
    • Placenta accreta: villi implant on the myometrial surface without intervening decidua
    • Placenta increta: villi extend into the myometrium
    • Placenta percreta: villi penetrate the entire myometrial thickness and through the uterine serosa
Terminology
  • Placenta creta
  • Morbidly adherent placenta (MAP)
ICD coding
  • ICD-10:
    • O43.21 - Placenta accreta
    • O43.22 - Placenta increta
    • O43.23 - Placenta percreta
    • O43.2 - Morbidly adherent placenta
Epidemiology
Sites
  • In order of frequency: uterus, lower uterine segment and cervix
  • Placenta percreta may extend to bladder, ureters and bowel
Pathophysiology
Etiology
  • Previous cesarean sections (a greater number of cesarean sections means a greater risk for accreta) (Pediatr Dev Pathol 2017;20:387)
  • Placenta previa
  • Prior uterine instrumentation
  • Submucosal leiomyoma
  • Asherman syndrome (scar tissue within uterine cavity)
Diagrams / tables

Images hosted on other servers:
Placenta accreta, increta and percreta

Placenta accreta, increta and percreta

Clinical features
  • Severe peripartum hemorrhage can occur if the placenta cannot be separated from the uterus at delivery (J Matern Fetal Neonatal Med 2016;29:1795)
  • Massive peripartum hemorrhage may lead to disseminated intravascular coagulation (DIC) and shock
  • Placenta percreta may damage adjacent organs, including bladder, ureters and bowel
Diagnosis
  • Often suspected on prenatal imaging studies and operative findings
  • Diagnosis is made upon examination of the hysterectomy specimen
    • Histologic confirmation is required
  • On rare occasions, diagnosis of placenta accreta can be made on the delivered placenta
Radiology description
  • Ultrasound: loss of normal hypoechoic retroplacental zone, increased subplacental vascularity, abnormal interface between uterus and bladder, retroplacental myometrial thickness < 1 mm, multiple vascular lacunae within the placenta (J Matern Fetal Neonatal Med 2016;29:1795)
  • MRI may be helpful, particularly < 30 weeks gestation
  • Prenatal imaging is more sensitive at detecting severe cases of accreta and tends to not identify mild forms
Radiology images

Images hosted on other servers:
Ultrasound suspicious for placenta accreta

Ultrasound suspicious for placenta accreta

Ultrasound Doppler of placenta percreta

Ultrasound Doppler of placenta percreta

Ultrasound Doppler of placenta accreta

Ultrasound Doppler of placenta accreta

Prognostic factors
  • Delayed placental separation or manual removal increases the risk for accreta in future pregnancies
  • Presence of extensive myometrial fibers adherent to the basal plate in a delivered placenta has been shown to increase the risk of placenta accreta in subsequent pregnancies (BJOG 2016;123:2140)
Case reports
Treatment
  • Massive peripartum hemorrhage needs immediate treatment with blood transfusions and management of disseminated intravascular coagulation and shock
  • Emergent hysterectomy is required if bleeding cannot be controlled
  • Elective hysterectomy may be planned if imaging studies are concerning for severe forms of abnormal placental implantation
  • Conservative options include uterine artery ligation, balloon tamponade, uterotonics and hysteroscopic resection for mild forms (Am J Obstet Gynecol 2015;213:755)
Clinical images

Images hosted on other servers:

Intraoperative findings of placenta percreta

Intraoperative findings of placenta accreta

Gross description
  • Hysterectomy specimen:
    • With placenta in situ:
      • Placenta accreta: placenta adherent to the uterine wall; myometrium not thinned
      • Placenta increta: placenta extends into the uterine wall, usually in a blunt manner; myometrium thinned
      • Placenta percreta: placenta penetrates through the uterine or lower uterine segment wall; protruding placental tissue on external surface (should be inked) and adherent structures (bladder, bowel)
      • Note where the placenta is implanted (lower uterine segment implantation / placenta previa is common)
    • With separate placenta:
      • Placental implantation site may or may not be visible
      • Increased vascularity with ectatic vessels on superficial myometrium provide a clue for the placental implantation site
        • If visible, this area should be sampled
        • If not visible, check medical records for site of placental implantation and sample the area indicated
    • Refer to published guidelines on how to perform gross examination and sampling (Arch Gynecol Obstet 2016;293:951)
  • Delivered placenta:
    • Disruption of basal plate
    • Missing cotyledons in some cases
    • Higher yield of identifying adherent myometrial fibers microscopically by sampling the intact basal plate adjacent to disrupted areas
Gross images

Contributed by Fabiola Medeiros, M.D.
Placenta accreta

Placenta accreta

Placenta increta

Placenta increta

Placenta previa and percreta

Placenta previa and percreta

Placenta previa and percreta adherent to bladder

Placenta previa and percreta adherent to bladder

Disrupted manually removed placenta

Disrupted manually removed placenta

Microscopic (histologic) description
  • Diagnosis traditionally made on hysterectomy specimen
    • Placenta accreta:
      • Chorionic villi implant directly on the surface of the myometrium without intervening decidua
      • Fibrin and extravillous trophoblast (EVT) are often present between the villi and myometrial fibers, in which case a diagnosis of accreta should still be made, given that intervening decidua is not present
      • Differentiating decidual cells and extravillous trophoblastic cells may be difficult
      • Myometrium is not thinned
    • Placenta increta:
      • Chorionic villi identified within the myometrium
      • Fibrin and extravillous trophoblast can be present between the villi and myometrial fibers
      • Myometrium is thinned
      • Presence of extravillous trophoblast within the myometrium is not a diagnostic feature of placenta increta
    • Placenta percreta:
      • No residual myometrium
      • Ink present on villous tissue obtained from area suspicious for placenta percreta grossly
        • It is critical that invasion through the myometrial wall is identified in this area to exclude the possibility that the protruding placental tissue was displaced during surgery through the cesarean section incision
      • Villous tissue adjacent to adipocytes or in extrauterine structures, such as bladder, is seen in some cases and is diagnostic of percreta
  • Diagnosis uncommonly made on delivered placenta (occult placenta accreta)
    • Myometrial fibers attached to the basal plate with complete lack of intervening decidua between the myometrial fibers and the basal chorionic villi, with or without intervening fibrin / extravillous trophoblast (BJOG 2016;123:2140)
    • A staging system has been proposed but is not currently used in most practices (Placenta 2015;36:1419)
Microscopic (histologic) images

Contributed by Fabiola Medeiros, M.D.
Placenta accreta Placenta accreta

Placenta accreta

Trophoblastic versus decidual cells

Trophoblastic versus decidual cells

Placenta increta

Placenta increta

Placenta percreta

Placenta percreta

Occult placenta accreta

Occult placenta accreta

Virtual slides

Images hosted on other servers:
Placenta increta

Placenta increta

Cervical implantation of placenta

Cervical implantation of placenta

Positive stains
  • Immunohistochemistry is not required for diagnosis
  • Keratins and GATA3 are positive in extravillous trophoblast
  • Vimentin and CD10 are positive in decidual cells
Videos

Introduction to placenta accreta

Sample pathology report
  • Uterus and placenta, postcesarean supracervical hysterectomy:
    • Placenta accreta
    • Placental parenchyma, fetal membranes and trivascular cord with no significant histopathologic abnormalities
    • Myometrium and uterine serosa with no significant abnormalities
    • Endocervix with no significant abnormalities, no ectocervix identified
  • Uterus, cervix and placenta, postpartum total hysterectomy:
    • Placenta previa and percreta
    • Placenta adherent to serosa of urinary bladder but no involvement of bladder mucosa / muscular wall
    • Very preterm placenta (30 4/7 weeks), fetal membranes and trivascular umbilical cord
Differential diagnosis
  • Placenta protruding through the cesarean section defect versus placenta percreta:
    • Careful gross examination reveals that the protruding placental tissue is at the site of the cesarean section
    • Look for sutures at the site
    • Not true percreta
    • Correlate with operative note
  • Normally thinned myometrium at lower uterine segment versus placenta increta:
    • Compare the thickness of the lower uterine segment at the side suspicious for increta with the thickness of the lower uterine segment on the opposite side
    • If the myometrium of both sides has a similar thickness throughout, it is not increta
  • Physiologic invasion of extravillous trophoblast into the myometrium versus placenta accreta:
    • Extravillous trophoblast normally infiltrates the inner third of the myometrium and this is not accreta
    • In accreta, only extravillous trophoblast without decidual cells are present between villi and myometrium
  • Extravillous trophoblast versus decidual cells:
    • Both are large polygonal cells with abundant eosinophilic cytoplasm
    • Decidual cells have uniformly bland nuclei with smooth nuclear membranes, homogenous open chromatin and small nucleoli
    • Extravillous trophoblast cells have atypical nuclei with irregular nuclear membranes, variation in nuclear shape and size and often hyperchromatic or irregular chromatin
Board review style question #1

A 38 year old woman G3 P2 underwent a peripartum hysterectomy for life threatening uncontrollable vaginal bleeding. On gross examination, the placenta was in situ and the thickness of the myometrium was markedly decreased at the placental implantation site. The uterine serosa and lower uterine segment were grossly unremarkable. Microscopic examination revealed villi juxtaposed to myometrial fibers. What is the most appropriate diagnosis?

  1. Placenta accreta
  2. Placenta increta
  3. Placenta percreta
  4. Subinvolution of the placental site
  5. Uterine atony
Board review style answer #1
Board review style question #2
Which of the following is required for a diagnosis of placenta accreta?

  1. Absence of intervening decidua between villi and myometrium
  2. Invasive extravillous trophoblast into the myometrium
  3. Myometrial fibers adherent to the basal plate
  4. Placenta grossly adherent to the uterine wall
  5. Villous invasion through the myometrium and serosa
Board review style answer #2
A. Absence of intervening decidua between villi and myometrium

Comment Here

Reference: Placenta accreta, increta and percreta
Back to top
Image 01 Image 02