Placenta
Infectious conditions
Chorioamnionitis

Editorial Board Member: Jennifer Bennett, M.D.
Editor-in-Chief: Debra Zynger, M.D.
Erdener Özer, M.D., Ph.D.

Topic Completed: 29 October 2019

Revised: 29 October 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Placenta chorioamnionitis[TI] free full text[sb]

Erdener Özer, M.D., Ph.D.
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Cite this page: Özer E. Chorioamnionitis. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/placentachorioamnionitis.html. Accessed November 21st, 2019.
Definition / general
  • Inflammation of the amniochorionic membranes of the placenta in response to microbial invasion
  • Diffuse maternal infiltration of the chorion or subchorionic fibrin by neutrophils originating in the intervillous space or decidual postcapillary venules (maternal inflammatory response)
Essential features
  • Due to maternal inflammatory response
  • Tissue evaluation is gold standard for the diagnosis of amniotic fluid infection
  • Often associated with maternal ascending infection, preterm premature rupture of membranes and spontaneous preterm birth
  • Higher risk of neonatal sepsis and fetal central nervous system injury
  • Sometimes associated with fetal inflammatory response, including chorionic vasculitis and funisitis
Terminology
  • Acute chorioamnionitis
  • Histologic chorioamnionitis
  • Chorionitis
  • Subchorionitis
  • Subacute chorioamnionitis
ICD coding
  • ICD-10: O41.1230 - chorioamnionitis, third trimester, not applicable or unspecified
Epidemiology
Sites
  • Chorion or subchorion
Pathophysiology
Etiology
  • 2 or more microbes are common
  • Usually due to ascending bacterial infection caused by the genital mycoplasmas such as Ureaplasma urealyticum and Mycoplasma hominis, anaerobes such as Gardnerella vaginalis and Bacteriodes, aerobes such as group B Streptococcus and Escherichia coli and Fusobacterium nucleatum (PLoS One 2017;12:e0180167, Clin Perinatol 2010;37:339)
  • Subacute chorioamnionitis is due to longstanding infection by pathogens of low virulence
  • Chronic chorioamnionitis: etiology unknown, usually seen in late preterm birth, unusual to histologically diagnose (Placenta 2013;34:681)
Diagrams / tables

Contributed by Erdener Özer, M.D., Ph.D.

Histologic chorioamnionitis

Clinical features
  • Usually clinically silent
  • Maternal fever > 37.5 °C, uterine tenderness, abdominal pain, foul smelling vaginal discharge, maternal and fetal tachycardia (BJOG 2017;124:775)
  • Associated with fetal infection, neonatal sepsis, stillbirth, spontaneous preterm birth and fetal central nervous system injury (Semin Perinatol 2015;39:2)
  • Fetal inflammatory response associated with multiorgan injury, including chronic lung disease, periventricular leukomalacia and cerebral palsy (Clin Perinatol 2010;37:339)
Staging and grading
  • Amsterdam consensus criteria can be used to stage and grade the maternal and fetal inflammatory responses in ascending intrauterine infection (Arch Pathol Lab Med 2016;140:698)
  • Maternal inflammatory response
    • Stage 1: acute subchorionitis or chorionitis
    • Stage 2: acute chorioamnionitis (polymorphonuclear leukocytes extend into fibrous chorion or amnion)
    • Stage 3: necrotizing chorioamnionitis (karyorrhexis of polymorphonuclear leukocytes, amniocyte necrosis or amnion basement membrane hypereosinophilia)
    • Grade 1: not severe (as defined below)
    • Grade 2: severe (confluent polymorphonuclear leukocytes or with subchorionic microabscesses)
  • Fetal inflammatory response
    • Stage 1: chorionic vasculitis or umbilical phlebitis
    • Stage 2: involvement of the umbilical vein and one or more umbilical arteries
    • Stage 3: necrotizing funisitis
    • Grade 1: not severe (as defined below)
    • Grade 2: severe (near confluent intramural polymorphonuclear leukocytes with attenuation of vascular smooth muscle)
Diagnosis
  • Clinical signs and symptoms
  • Laboratory tests including white blood cell count, other blood tests and amniotic fluid testing (Clin Perinatol 2010;37:339)
  • Histologic evaluation of the placenta
Laboratory
Prognostic factors
Case reports
Treatment
  • Maternal and neonatal antibiotic therapy
Gross description
  • Dull, opaque membranes with yellow-green discoloration and cloudy amniotic fluid, possibly with purulent exudate
  • Seldom grossly normal
  • Acute marginal hemorrhage in preterm deliveries (ISRN Obstet Gynecol 2012;2012:856971)
  • Multifocal abscesses in C. albicans infections (APMIS 2018;126:570)
Gross images

Contributed by Erdener Özer, M.D., Ph.D.

Chorioamnionitis in term placenta

Chorioamnionitis in twin placenta

C. albicans associated chorioamnionitis

Microscopic (histologic) description
  • Neutrophilic infiltrate of membranes and those overlying the chorionic plate
  • Variable fetal inflammatory response including chorionic plate vasculitis, umbilical phlebitis, umbilical arteritis and umbilical concentric perivasculitis
  • Subacute chorioamnionitis
    • Mixed cell infiltrate of mononuclear cells (usually macrophages) and neutrophils, primarily in the amnion and upper chorion, and polarization of mononuclear cells towards the amnion
    • Amniotic necrosis (stage 3)
  • Sometimes accompanied by acute intervillositis (often due to Listeria monocytogenes), peripheral funisitis (often due to Candida) and acute deciduitis in preterm deliveries
  • Chronic chorioamnionitis
    • Primarily lymphocytic infiltration of chorioamnion
Microscopic (histologic) images

Contributed by Erdener Özer, M.D., Ph.D.

Acute subchorionitis (stage 1)

Acute chorioamnionitis (stage 2)

Necrotizing chorioamnionitis (stage 3)


Acute chorioamnionitis (mild)

Acute subchorionitis (severe)

Subacute chorioamnionitis

Chronic chorioamnionitis

Chorionic plate vasculitis

Umbilical concentric perivasculitis


C. albicans chorioamnionitis

Positive stains
  • PAS and GMS for demonstrating blastospore and hyphal forms of Candida species
Negative stains
Sample pathology report
  • Placenta, delivery:
    • Acute chorioamnionitis
Board review question #1
A 25 year old pregnant woman presented with uterine tenderness, abdominal pain and foul smelling vaginal discharge. The pathological examination of the placental membranes revealed multifocal abscess and severe acute inflammation. GMS stained section is below. Which of the following pathogens is most likely to cause chorioamnionitis?



  1. Actinomyces
  2. Aspergillus
  3. Candida albicans
  4. Cryptococcus
  5. Histoplasma
Board review answer #1
C. Candida albicans. Fungal infections rarely cause chorioamnionitis. C. albicans is the most common yeast isolated from the vagina in both symptomatic and asymptomatic patients. Multifocal abscesses are common. GMS staining demonstrates hyphal forms.

Reference: Placenta - Chorioamnionitis

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Board review question #2
Which of the following is related to the maternal inflammatory response in chorioamnionitis?

  1. Acute subchorionitis
  2. Deciduitis
  3. Chorionic vasculitis
  4. Intervillitis
  5. Umblical phlebitis
Board review answer #2
A. Acute subchorionitis. Maternal inflammatory response in chorioamnionitis include acute subchorionitis or chorionitis, acute chorioamnionitis and necrotizing chorioamnionitis, in contrast to chorionic vasculitis, umbilical phlebitis and necrotizing funisitis, which are the findings of fetal inflammatory response.

Reference: Placenta - Chorioamnionitis

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