Definition/General
Introduction:
Placental chorioamnionitis is the inflammatory infiltration of the fetal membranes and umbilical cord
It represents the histological counterpart of clinical chorioamnionitis
The condition involves ascending bacterial infection from the lower genital tract
It occurs in 10-20% of term deliveries
Higher incidence in preterm births (40-70%).
Origin:
Results from ascending infection through the cervix
Bacterial colonization of amniotic fluid
Maternal inflammatory response in chorion and decidua
Fetal inflammatory response in umbilical vessels
Hematogenous seeding less common.
Classification:
Staged by location and severity: Stage 1: subchorionitis/chorionitis
Stage 2: chorioamnionitis
Stage 3: necrotizing chorioamnionitis
Maternal response vs fetal response
Acute vs chronic inflammation.
Epidemiology:
Incidence: 10-20% term pregnancies
40-70% preterm births
More common with prolonged rupture of membranes
Associated with preterm labor
Neonatal sepsis in 2-13% cases.
Clinical Features
Presentation:
Maternal fever (>38°C)
Maternal tachycardia (>100 bpm)
Fetal tachycardia (>160 bpm)
Uterine tenderness
Malodorous amniotic fluid
Maternal leukocytosis
Preterm labor.
Symptoms:
Fever and chills
Abdominal pain
Malodorous discharge
Uterine contractions
Nausea and vomiting
General malaise.
Risk Factors:
Prolonged rupture of membranes (>18 hours)
Prolonged labor
Multiple vaginal examinations
Internal fetal monitoring
Meconium-stained fluid
Maternal GBS colonization
Young maternal age
Substance abuse.
Screening:
Clinical criteria (fever, tachycardia, leukocytosis)
Laboratory tests: CBC, CRP
Amniotic fluid analysis (if indicated)
Blood cultures
Fetal monitoring.
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Gross Description
Appearance:
Opaque, thickened membranes
Yellow-green discoloration
Purulent exudate on surfaces
Friable, easily torn membranes
Foul odor may be present
Umbilical cord may appear inflamed.
Characteristics:
Loss of membrane translucency
Increased thickness
Surface exudate
Congested vessels
Edematous cord.
Size Location:
Diffuse involvement of membranes
Placental surface changes
Umbilical cord inflammation
Maternal surface may show purulence.
Multifocality:
Usually diffuse process
May be focal initially
Progressive extension
Associated with funisitis.
Microscopic Description
Histological Features:
Neutrophilic infiltration of membranes
Maternal inflammatory response: chorion/decidua
Fetal inflammatory response: umbilical vessels
Stromal edema
Vascular congestion
Necrosis in severe cases.
Cellular Characteristics:
Neutrophils predominant in acute phase
Macrophages and lymphocytes
Plasma cells in chronic cases
Bacterial organisms may be visible
Degenerative changes in amnion.
Architectural Patterns:
Subchorionic space infiltration (stage 1)
Chorioamniotic infiltration (stage 2)
Necrotizing inflammation (stage 3)
Umbilical vessel wall infiltration
Concentric zones of inflammation.
Grading Criteria:
Maternal response: Stage 1-3
Fetal response: Grade 1-3
Acute: neutrophilic
Chronic: lymphoplasmacytic
Severity assessment: mild, moderate, severe.
Immunohistochemistry
Positive Markers:
CD68 (macrophages)
CD45 (leukocytes)
Myeloperoxidase (neutrophils)
CD3 (T-lymphocytes)
CD20 (B-lymphocytes)
Cytokeratin (amnion epithelium).
Negative Markers:
Specific pathogens require special stains
Gram stain for bacteria
PAS for fungi
Silver stains for organisms.
Diagnostic Utility:
Limited routine use
Research applications
Special stains for organisms
Immunophenotyping inflammatory cells.
Molecular Subtypes:
Bacterial chorioamnionitis
Viral chorioamnionitis
Fungal chorioamnionitis
Sterile inflammation.
Molecular/Genetic
Genetic Mutations:
Host genetic factors
Cytokine gene polymorphisms
Toll-like receptor variants
Complement system genes
Immunoglobulin variants.
Molecular Markers:
Pro-inflammatory cytokines (IL-1β, TNF-α, IL-6)
Chemokines (IL-8)
Acute phase reactants (CRP)
Matrix metalloproteinases
Prostaglandins.
Prognostic Significance:
Severity correlates with neonatal outcomes
Fetal inflammatory response worse prognosis
Funisitis increases morbidity
Necrotizing inflammation severe complications.
Therapeutic Targets:
Antibiotic therapy
Early delivery
Neonatal antibiotics
Anti-inflammatory agents (experimental)
Supportive care.
Differential Diagnosis
Similar Entities:
Chronic villitis
Decidual vasculopathy
Meconium-associated changes
Maternal floor infarction
Subchorionic hematoma.
Distinguishing Features:
Chorioamnionitis: Membrane inflammation
Neutrophilic infiltrate
Clinical correlation
Villitis: Villous inflammation
Lymphocytic infiltrate
Meconium: Pigmented macrophages
No neutrophils.
Diagnostic Challenges:
Mild inflammation vs normal
Chronic vs acute
Sterile inflammation
Post-mortem changes
Sampling issues.
Rare Variants:
Chronic chorioamnionitis
Granulomatous inflammation
Eosinophilic chorioamnionitis
Candidal chorioamnionitis.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
Placenta with membranes showing inflammatory changes
Diagnosis
Acute chorioamnionitis
Clinical Correlation
Maternal fever, prolonged rupture of membranes [X] hours
Membrane Examination
Opaque, thickened membranes with purulent exudate
Microscopic Findings
Neutrophilic infiltration of chorioamniotic membranes
Maternal Response
Stage [1/2/3] chorioamnionitis
Fetal Response
Funisitis: [present/absent], Grade [1-3] if present
Severity Assessment
[Mild/Moderate/Severe] acute inflammation
Microbiological Findings
Culture results: [organism/sterile/pending]
Final Diagnosis
Acute chorioamnionitis, Stage [X], with/without funisitis