Definition/General
Introduction:
Subchorionic hematoma is characterized by blood collection between the chorion and decidua
It occurs in the subchorionic space
It represents localized placental separation
It is associated with first trimester bleeding.
Origin:
Results from partial placental detachment
Spiral artery rupture into subchorionic space
Decidual vessel bleeding
Trauma or increased uterine pressure
Abnormal trophoblastic invasion
May be spontaneous or traumatic.
Classification:
Classified by size: Small (<20% of gestational sac), Large (≥20%)
By gestational age: First trimester vs later pregnancy
By outcome: Resolving vs expanding
Location-based: Marginal vs central.
Epidemiology:
Incidence approximately 1-3% of pregnancies
More common in first trimester
Detected in 20-25% of early pregnancy bleeding
Resolves spontaneously in 70-80% of cases
Risk increases with maternal age.
Clinical Features
Presentation:
Vaginal bleeding (most common)
Abdominal cramping
Pelvic pressure
May be asymptomatic (incidental ultrasound finding)
Threatened abortion presentation
Brown discharge (resolving hematoma).
Symptoms:
Spotting or heavy bleeding
Lower abdominal pain
Pelvic cramping
Back pain (some cases)
Anxiety due to bleeding
Passage of clots (large hematomas)
No fever (unless infected).
Risk Factors:
Advanced maternal age (>35 years)
History of miscarriage
Trauma during pregnancy
In vitro fertilization
Multiple gestation
Placental abnormalities
Uterine abnormalities.
Screening:
Transvaginal ultrasound (diagnostic)
Serial beta-hCG levels
Complete blood count
Coagulation studies (if indicated)
Pelvic examination
Follow-up ultrasounds to monitor resolution.
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Gross Description
Appearance:
Dark red to brown blood clot adherent to fetal membranes
Well-circumscribed hematoma
Variable size from few millimeters to several centimeters
Organized clot in chronic cases
May be partially liquefied.
Characteristics:
Firm, dark red clot
Adherent to chorion
Well-demarcated from surrounding tissue
Variable consistency depending on age
May show laminated appearance
Organization with time.
Size Location:
Size ranges from few millimeters to >5 cm
Located between chorion and decidua
May be marginal or central
Crescentic shape common
Can extend around gestational sac.
Multifocality:
Usually single location
May have multiple small hematomas
Confluent areas possible
Extension along choriodecidual interface
Geographic distribution in some cases.
Microscopic Description
Histological Features:
Acute hemorrhage with intact red blood cells
Fibrin deposition
Organization with granulation tissue formation
Hemosiderin-laden macrophages
Decidual reaction at margins
Chronic inflammatory infiltrate (organized hematomas).
Cellular Characteristics:
Fresh red blood cells (acute phase)
Hemosiderin-laden macrophages
Fibroblasts and capillaries (organizing phase)
Decidual cells at interface
Neutrophils (if secondarily infected)
Giant cells occasionally.
Architectural Patterns:
Layered appearance (repeated bleeding episodes)
Central liquefaction in large hematomas
Peripheral organization
Granulation tissue at margins
Interface with normal chorion
Capsule formation (chronic cases).
Grading Criteria:
Based on age of hematoma: Acute (<1 week), Subacute (1-4 weeks), Chronic (>4 weeks)
Size-based: Small, moderate, large
Organization degree: Fresh, organizing, organized.
Immunohistochemistry
Positive Markers:
CD68 (hemosiderin-laden macrophages)
Factor VIII (endothelial cells in organizing areas)
Smooth muscle actin (vessel walls)
CD34 (endothelial cells)
Fibrinogen/Fibrin.
Negative Markers:
Cytokeratin (distinguishes from trophoblast)
hCG (not expressed in hematoma)
Inflammatory markers in acute cases
Infectious organism stains.
Diagnostic Utility:
CD68 confirms macrophage presence
Factor VIII shows vascular organization
Distinguishes from other lesions
Assesses degree of organization
Rules out trophoblastic lesions.
Molecular Subtypes:
Not applicable for routine classification
Coagulation studies may reveal underlying disorders
Thrombophilia workup in recurrent cases.
Molecular/Genetic
Genetic Mutations:
Usually no specific genetic mutations
Coagulation factor deficiencies may predispose
Thrombophilia mutations (rare association)
Platelet function disorders
Vascular malformation genes.
Molecular Markers:
Coagulation studies (PT, PTT, Fibrinogen)
Platelet count and function
D-dimer levels
Factor assays if indicated
von Willebrand factor studies.
Prognostic Significance:
Size correlates with outcomes
Large hematomas (>20% of sac) higher risk
Location affects prognosis (marginal vs central)
Early gestational age worse prognosis
Most resolve spontaneously.
Therapeutic Targets:
Conservative management most common
Pelvic rest
Activity modification
Close monitoring
Progesterone supplementation (controversial)
Intervention for complications.
Differential Diagnosis
Similar Entities:
Retroplacental hematoma (behind placenta)
Chorionic bump (localized thickening)
Molar pregnancy (early stages)
Decidual cyst
Uterine fibroid
Ovarian cyst.
Distinguishing Features:
Subchorionic: Between chorion and decidua
Subchorionic: Crescentic shape
Retroplacental: Behind placental mass
Molar: Trophoblastic proliferation
Decidual cyst: Cystic appearance
Fibroid: Myometrial location.
Diagnostic Challenges:
Distinguishing from other causes of bleeding
Small hematomas may be missed
Correlation with ultrasound
Dating the age of hematoma
Ruling out molar pregnancy.
Rare Variants:
Infected subchorionic hematoma
Calcified chronic hematoma
Multiple discrete hematomas
Combined with retroplacental bleeding
Extending subchorionic hematoma.
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
Products of conception with [size] subchorionic hematoma measuring [dimensions]
Diagnosis
Subchorionic Hematoma
Classification
Classification: [Small/Large] [acute/subacute/chronic] subchorionic hematoma
Histological Features
Shows [fresh/organizing/organized] hemorrhage in subchorionic space with [degree] of organization
Age Assessment
Hematoma age: [acute/subacute/chronic] based on histological features
Organization Degree
Organization: [minimal/moderate/extensive] with [granulation tissue/fibrosis] formation
Complications
Complications: [none identified/secondary infection/extension]
Clinical Correlation
Findings correlate with [clinical presentation]. Size and location consistent with [prognosis].
Final Diagnosis
Subchorionic Hematoma, [size], [age], with [organization degree] and [clinical significance]