Placental Infections

Slide 1 · Placental Infections

Mechanisms, morphology, and fetal consequences

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · What the pathology should explain

Distinguish ascending infection from hematogenous transplacental spread.

Localize inflammation to membranes, fetal vessels, or chorionic villi.

Connect maternal and fetal inflammatory patterns with clinically relevant outcomes.

Interpret TORCH-associated villitis without assuming an organism from morphology alone.

Slide 3 · Why examine the infected placenta?

Placental pathology can help explain adverse pregnancy or perinatal outcomes.

The distribution of inflammation provides information about how an infection reached the placenta.

Maternal and fetal responses are anatomically distinct and should be separately described.

An inflammatory lesion is not, by itself, proof of a particular pathogen or outcome.

Slide 4 · Three placental compartments to recognize

Fetal membranes

Fetal vascular structures

Chorionic villi

Membranes favor an ascending process; Fetal vessels record a fetal response; Villitis points toward villous inflammation.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 5 · Chorionic villi are the exchange surface

Maternal intervillous blood

Fetal capillary

Villous stroma

Trophoblast boundary

Fetal blood remains in villous capillaries

Slide 6 · Trophoblast separates blood compartments

Syncytiotrophoblast and cytotrophoblast cover chorionic villi.

Fetal capillaries lie within villous stroma.

Maternal blood bathes the outside of the villi in the intervillous space.

This interface normally permits exchange without extensive direct mixing of fetal and maternal blood.

Slide 7 · Maternal and fetal circulations follow different paths

Maternal circulation

Intervillous exchange

Fetal capillary circulation

Exchange occurs across the villous boundary; The two bloodstreams do not normally mix freely.

Schematic circulation map — anatomy is simplified.

Slide 8 · An exchange barrier is not an absolute infection barrier

Maternal bloodstream

Placental interface

Villous / fetal compartment

Hematogenous infection may reach the placental exchange structures despite normal separation of circulating blood.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 9 · Two major pathways of placental infection

Feature

Ascending

Hematogenous

Initial source

Birth canal / lower genital tract

Maternal blood during sepsis, viremia, or parasitemia

Typical early location

Membranes and amniotic compartment

Chorionic villi

Characteristic inflammatory pattern

Acute maternal neutrophilic chorioamnionitis

Often chronic villitis; some bacterial cases show acute villitis

Slide 10 · Ascending infection begins below the membranes

Lower genital tract

Cervix / birth canal

Membranes and amniotic fluid

This as the more common route of placental infection.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 11 · Why ascending infections are usually bacterial

The typical ascending route is through the birth canal.

Ascending placental infections as virtually always bacterial.

The organism reaches membranes locally rather than requiring maternal bloodstream dissemination.

Pattern recognition should begin with route and site—not with a presumed species.

Slide 12 · Membrane anatomy determines the first lesion

Amniotic surface

Amnion

Chorion

Maternal decidual side

Simplified anatomic schematic; Colored layers do not represent H&E staining.

Slide 13 · Acute chorioamnionitis: The maternal lesion

Acute chorioamnionitis involves inflammatory cells in chorion and amnion.

The inflammatory cells emphasized by Robbins are maternal neutrophils.

Inflammation may be appreciable in the membranes even without a demonstrable organism on routine sections.

The tissue compartment determines whether an observation describes maternal or fetal response.

Slide 14 · Cloudy fluid and exudate: Gross correlates

Cloudy amniotic fluid with a purulent exudate.

Gross abnormalities are helpful clues but are not a complete microscopic diagnosis.

Correlate the gross appearance with the membrane histology.

Record what is observed rather than inferring a specific microbial cause from discoloration.

Slide 15 · Neutrophils in the membranes: Schematic topography

Amniotic surface

Amnion

Chorion

Maternal decidual side

Neutrophils within fetal membranes

Simplified anatomic schematic; Colored layers do not represent H&E staining.

Slide 16 · Maternal inflammatory response is defined by origin

The maternal response is an acute neutrophilic infiltrate in the chorion–amnion.

It reflects inflammation at the membranes after ascending exposure.

It is anatomically different from neutrophilic inflammation of fetal vessels.

Do not equate the presence of maternal inflammation with confirmed fetal inflammatory involvement.

Slide 17 · From membrane infection to membrane rupture

Ascending bacterial infection

Local membrane inflammation

Premature rupture of membranes

Premature membrane rupture as an important consequence in many ascending infections.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 18 · From membrane infection to preterm delivery

Membrane infection

Inflammatory obstetric complication

Preterm delivery

Infection-associated preterm birth is a clinically important pathway, but the route does not determine the outcome in every case.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 19 · Maternal response and fetal response are not synonyms

Feature

Maternal inflammatory response

Fetal inflammatory response

Principal compartment

Chorion and amnion

Umbilical cord and/or chorionic plate fetal vessels

Cells emphasized

Maternal neutrophils

Inflammation of fetal vascular walls

Interpretive role

Evidence of membrane inflammation

Evidence that inflammation involves the fetal vascular compartment

Slide 20 · Umbilical vasculitis records a fetal response

Two umbilical arteries

One umbilical vein

Inflammatory cells involving fetal vessel walls → fetal inflammatory response

Slide 21 · Chorionic plate vessels can also respond

Fetal chorionic plate vessels are part of the fetal placental circulation.

Their involvement is a second site of the fetal vascular inflammatory response.

The fetal response may be seen in the umbilical vessels, chorionic plate vessels, or both.

The location of an inflammatory infiltrate must be explicitly reported.

Slide 22 · How the two responses can coexist

Ascending infection

Neutrophils in membranes

Inflammation of fetal vessels

This is a conceptual progression, not a mandatory sequence for every affected placenta.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 23 · Clinical significance of intense fetal inflammation

Intense fetal inflammatory responses with increased perinatal morbidity.

An increased risk of later cerebral palsy is also noted.

This is a risk association—not proof that any individual placental lesion caused cerebral palsy.

Severity and fetal involvement should be interpreted alongside the clinical course.

Slide 24 · Why association is not individual-level causation

What placental histology supports

What it does not establish alone

A documented fetal vascular inflammatory response

A specific neurologic outcome in an individual infant

A pattern associated with elevated perinatal risk

That infection was the only contributor to morbidity

Anatomic evidence of inflammation

The precise species without appropriate microbiologic evidence

Slide 25 · One bacterium named in the broader source: Group B streptococcus

Streptococcus agalactiae (group B streptococcus) can colonize the female genital tract.

It as a cause of chorioamnionitis during pregnancy.

Group B streptococcal infection is also an important cause of neonatal sepsis and meningitis.

The organism is context for the ascending pathway; Histology alone does not identify group B streptococcus.

Slide 26 · Ascending pattern: An integrated interpretation

Maternal genital-tract source

Acute membrane inflammation

Potential fetal vessel response

Look for paired but separately described maternal and fetal inflammatory lesions.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 27 · Hematogenous infection starts with systemic maternal infection

Maternal infection

Pathogen in maternal bloodstream

Placental villous involvement

The source specifies maternal sepsis, viremia, and parasitemia as routes into the placenta.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 28 · Three systemic contexts for transplacental spread

Maternal systemic process

Potential placental exposure

Sepsis / bacteremia

Bacterial organisms in maternal blood

Viremia

Viruses circulating during maternal infection

Parasitemia

Parasites circulating during maternal infection

Slide 29 · Why the villus is a target in blood-borne infection

Maternal intervillous blood

Fetal capillary

Villous stroma

Trophoblast boundary

Potential pathogen approach

Route schematic only

Slide 30 · Acute villitis can occur after bacterial hematogenous spread

Bacteria can uncommonly reach the placenta by the hematogenous route.

This can produce acute inflammatory changes in chorionic villi.

A villous lesion must be distinguished from inflammation confined to extra-villous membranes.

An acute villous pattern does not identify the causative organism by itself.

Slide 31 · Chronic villitis is the dominant TORCH-type pattern

Chronic inflammatory cell infiltrates within chorionic villi.

This is the usual morphologic response to several hematogenously transmitted TORCH infections.

Chronic villitis concerns the villous parenchyma rather than only the chorion and amnion.

The morphologic category is broader than any single microbial diagnosis.

Slide 32 · Villitis and chorioamnionitis are different locations

Feature

Chorioamnionitis

Villitis

Tissue targeted

Fetal membranes: chorion and amnion

Chorionic villi

Common route in Robbins

Ascending infection

Hematogenous infection

Cell pattern emphasized

Maternal acute neutrophils

Often chronic inflammatory infiltrates

Principal inference

Membrane-centered process

Villous-parenchymal process

Slide 33 · Chronic villitis and fetal growth restriction

Blood-borne infection

Chronic villous inflammation

Association with growth restriction

The Robbins section reports this association; No numerical risk estimate is provided in the supplied section.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 34 · TORCH: The group identified

T: Toxoplasma infection.

O: Other infections, including syphilis, tuberculosis, and listeriosis in this section.

R: Rubella; C: Cytomegalovirus; H: Herpes simplex.

The mnemonic groups congenital pathogens; It does not imply identical histology or clinical behavior.

Slide 35 · TORCH agents have a shared route, not identical lesions

Shared feature

Important limitation

Maternal hematogenous spread can infect placenta

Microbial route does not guarantee the same pattern in all infections

Chronic villitis may be encountered

An individual villitis specimen may remain etiologically unclassified

Fetal growth restriction may accompany infection

No single outcome is inevitable

Slide 36 · Toxoplasma: Maternal infection can be vertically transmitted

Toxoplasma gondii is a parasitic protozoan.

Transmission to offspring can occur during active maternal infection in pregnancy.

Maternal infection can follow contaminated foods, water, soil, or oocyst exposure.

The placental lesson is transplacental passage from maternal infection—not a membrane-first bacterial process.

Slide 37 · Toxoplasma: Hematogenous pathway

Active maternal toxoplasmosis

Dissemination in maternal host

Potential fetal infection

The route is source-based; The diagram does not prescribe a fixed sequence of histologic events.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 38 · Congenital toxoplasmosis: Potential fetal effects

Fetal death or pregnancy loss as possible consequences.

Reported congenital manifestations include hydrocephalus and microcephaly.

Cerebral calcifications and chorioretinitis are further classic manifestations.

Clinical recognition may be delayed after birth.

Slide 39 · Syphilis: Transplacental infection

Treponema pallidum can cause congenital infection.

Congenital syphilis is most frequent in the setting of maternal primary or secondary disease.

The organisms circulate during these maternal disease stages.

It belongs to the “other” category of the TORCH grouping used by Robbins.

Slide 40 · Syphilis: Possible loss and infant disease

Untreated congenital syphilis may cause intrauterine or perinatal death.

Infantile manifestations include snuffles and desquamating or bullous rashes.

Hepatomegaly and skeletal abnormalities are described.

The placenta contributes to the diagnostic picture but does not replace organism-specific assessment.

Slide 41 · Syphilis: Diagnostic evidence must be specific

Placental pathology

Organism-specific laboratory evidence

Can document inflammatory placental involvement

Syphilis diagnosis uses serologic testing

Does not uniquely identify T. pallidum

Nontreponemal tests include RPR and VDRL

Requires clinical correlation

Treponemal tests provide specific antibody evidence

Slide 42 · Rubella: Congenital infection and embryopathy

Rubella is included in the TORCH group within the placental infection section.

Robbins also identifies rubella as an environmental infectious cause of congenital malformations.

Maternal vaccination has markedly reduced rubella embryopathy in high-resource settings.

The supplied placenta subsection does not specify a rubella-specific microscopic placental hallmark.

Slide 43 · Rubella: Separate fetal effects from villous morphology

What the source establishes

What it does not establish here

Rubella can be transmitted congenitally

An exclusive pathognomonic placental pattern

Congenital rubella may produce embryopathy

A diagnostic cell inclusion in every infected placenta

The organism is in the TORCH grouping

A specific histologic sensitivity or specificity

Slide 44 · CMV: Transplacental infection can affect fetal development

Cytomegalovirus is one of the named TORCH pathogens.

Congenital infection occurs after infection acquired in utero.

A spectrum from asymptomatic infection to cytomegalic inclusion disease.

Placental villitis and viral cytopathic changes can provide morphologic clues.

Slide 45 · CMV: Characteristic cytopathic morphology

CMV-infected cells may become enlarged.

Large basophilic intranuclear inclusions with a surrounding clear halo are characteristic.

Smaller cytoplasmic inclusions may also be seen.

These are organism-associated cytopathic changes; Generic chronic villitis is less specific.

Slide 46 · CMV within a villus: Site and cell change

Maternal intervillous blood

Fetal capillary

Villous stroma

Trophoblast boundary

Illustrative enlarged infected cell

Slide 47 · Congenital CMV: Early clinical manifestations

Affected newborns may show growth restriction and jaundice.

Hepatosplenomegaly, anemia, and thrombocytopenia-associated bleeding are described.

Brain abnormalities can include microcephaly and focal calcification in severe cases.

The neonatal syndrome is not required for placental infection to be present.

Slide 48 · Congenital CMV: Later consequences

Hearing loss and neurologic impairment may persist among affected survivors.

Some congenital infections are initially clinically silent.

Delayed neurologic sequelae may become apparent months or years later.

Placental findings and neonatal evaluation answer related but different questions.

Slide 49 · Congenital versus perinatal CMV

Congenital infection

Perinatal infection

Acquired in utero

Acquired during passage through birth canal or via breast milk

May cause fetal growth/developmental effects

Usually asymptomatic in the setting described by Robbins

Prenatal pathology may be relevant

Transmission may occur after placental development

Slide 50 · HSV: TORCH membership without a specified placental signature

Herpes simplex is named in the TORCH grouping.

The supplied placental subsection presents the hematogenous infection framework.

It does not describe a distinct, pathognomonic HSV placental lesion.

Do not diagnose HSV from nonspecific chronic villitis alone.

Slide 51 · Listeria: A significant bacterial exception

Listeria monocytogenes is a gram-positive, facultatively intracellular bacillus.

Pregnancy is a setting of increased vulnerability to serious listeriosis.

Listeria can involve the placenta through a systemic maternal infection.

The named organism illustrates why hematogenous spread is not restricted to viruses or parasites.

Slide 52 · Listeriosis in pregnancy: Consequences

Maternal listeriosis is often food-borne.

Pregnancy-associated listeriosis with amnionitis.

Reported complications include pregnancy loss, stillbirth, and neonatal sepsis.

Placental inflammation should be interpreted with maternal and neonatal microbiology.

Slide 53 · Listeria: Acute necrotizing intervillositis

Neutrophils in intervillous spaces

Villi shown schematically

Conceptual intervillositis schematic — not a microscopy image.

Slide 54 · Intervillositis differs from villitis

Intervillositis

Villitis

Intervillous space between villi

Inside the villous tissue

Inflammatory cells occupy maternal blood space

Inflammatory cells infiltrate villous stroma

Listeria figure illustrates an acute necrotizing example

TORCH section emphasizes chronic villitis

Slide 55 · Pathogen and lesion: A discriminating comparison

Infectious context

Source-described placental pattern

Typical ascending bacterial infection

Acute neutrophilic membrane inflammation ± fetal vasculitis

Common TORCH-type blood-borne infection

Chronic villitis

Occasional blood-borne bacterial infection

Acute villitis

Listeria example in figure 22.50

Acute necrotizing intervillositis

CMV example in figure 22.50

Villous cells with viral inclusions

Slide 56 · Start an interpretation with anatomic localization

Which compartment?

Which inflammatory response?

Which maternal / fetal context?

Anatomic localization precedes etiologic attribution, because many infectious processes share inflammatory patterns.

Original editable mechanism schematic — direction denotes the described route or interpretive sequence.

Slide 57 · What the pathology report can legitimately state

The lesion and its distribution: Membranes, cord vessels, chorionic plate, villi, or intervillous space.

Whether the findings represent maternal inflammation, fetal inflammation, or both.

Whether a distinctive cytopathic clue such as CMV inclusion is visible.

The need for clinical and microbiologic correlation when morphology is nonspecific.

Slide 58 · What the histology cannot safely decide alone

A unique pathogen identity in every case of acute inflammation.

That TORCH-type chronic villitis automatically establishes a congenital infection.

The precise probability of growth restriction or neurologic injury from an individual lesion.

Whether maternal and infant clinical manifestations share one confirmed organism without direct evidence.

Slide 59 · Case application: Acute inflammation in fetal membranes

Illustrative teaching vignette

A preterm delivery follows premature membrane rupture. The placenta shows neutrophils in the chorion and amnion.

Which route and inflammatory compartment are most strongly suggested?

Slide 60 · Case interpretation: Membrane-centered inflammation

An ascending process is most consistent with the membrane-centered distribution.

Maternal neutrophils support an acute maternal inflammatory response.

The described lesion does not establish fetal vessel inflammation unless it is observed.

No specific bacterial species can be concluded from the morphology alone.

Slide 61 · Case application: Fetal vascular inflammation

Illustrative teaching vignette

A placenta shows acute chorioamnionitis and inflammatory infiltrates involving umbilical vessel walls.

Which additional inflammatory response is present, and what clinical caveat applies?

Slide 62 · Case interpretation: Fetal response

Umbilical vessel vasculitis supports a fetal inflammatory response.

It is distinct from the maternal neutrophilic response in membranes.

Intense fetal inflammation is associated with perinatal morbidity and elevated cerebral palsy risk.

Risk association is not individual proof of neurologic causation.

Slide 63 · Case application: Chronic villitis and growth restriction

Illustrative teaching vignette

A placenta from a pregnancy affected by fetal growth restriction contains chronic inflammatory infiltrates in chorionic villi.

Which broad infection route is relevant, and what should not be concluded from villitis alone?

Slide 64 · Case interpretation: Villitis requires etiologic correlation

The distribution raises consideration of hematogenous infection.

Several TORCH-type agents may be associated with chronic villitis and growth restriction.

Chronic villitis is not specific for any one TORCH organism.

Additional history, clinical testing, and direct evidence are needed for etiologic diagnosis.

Slide 65 · A diagnostic synthesis: Location, cells, and consequence

Finding

Interpretive implication

Membrane neutrophils

Maternal acute response; usually ascending

Fetal vessel inflammation

Fetal inflammatory response

Chronic villous infiltrates

Consider blood-borne TORCH-type process

Intranuclear CMV-type inclusions

Specific viral cytopathic clue

Neutrophilic intervillositis and villous necrosis

Compatible with described Listeria example; not etiologic proof alone

Slide 66 · Four principles to retain

Route matters: Ascending infections are most common; Hematogenous infections have a different initial source.

Location matters: Membranes, fetal vessels, villi, and intervillous spaces are not interchangeable.

Morphology matters: Acute neutrophilic inflammation, chronic villitis, and viral cytopathic changes convey different information.

Inference has limits: Clinical correlation and organism-specific evidence remain essential.

Slide 67 · Primary sources and visual provenance

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. (2026). Ch 22, “Gestational and Placental Disorders,” pp 934 and 937.

Same textbook, Ch 8: CMV (pp 323–324), group B streptococcus (p 327), listeriosis (p 329), congenital syphilis (p 343), toxoplasmosis (pp 360–361).

Same textbook, Ch 10: congenital anomalies / congenital rubella (pp 413–414).

All visuals in this presentation are original editable conceptual schematics; they are not histologic specimens or reproduced textbook figures.