Chorioamnionitis: Symptoms, Types, Causes and Treatment

Chorioamnionitis is a significant complication in pregnancy, posing risks for both mother and baby. While it is commonly linked to infection or inflammation of the fetal membranes (chorion and amnion), recent research reveals a complex syndrome with variable presentations, multiple underlying causes, and diverse outcomes. Understanding the symptoms, types, causes, and evidence-based treatments is crucial for healthcare providers and expectant families alike.

Symptoms of Chorioamnionitis

Chorioamnionitis can be a subtle or dramatic illness. Recognizing its symptoms early is vital, but diagnosis remains challenging due to their nonspecific nature. Both mothers and fetuses can display warning signs, yet not every case will present the same way.

Symptom	Description	Patient Affected	Source
Fever	Elevated maternal body temperature	Mother	1 2 3
Maternal Tachycardia	Increased maternal heart rate	Mother	1 2 3
Fetal Tachycardia	Elevated fetal heart rate	Fetus	1 2 3
Uterine Tenderness	Pain on palpation of uterus	Mother	1 2 3
Odorous Vaginal Discharge	Foul-smelling amniotic fluid	Mother	1 2 3
Leukocytosis	Increased white blood cell count	Mother	1 2 3

Table 1: Key Symptoms of Chorioamnionitis

Overview of Chorioamnionitis Symptoms

Chorioamnionitis typically manifests during labor, though it can develop earlier. The most prominent and consistent symptom is maternal fever, often above 38°C (100.4°F) 1 2 3. However, fever alone is not sufficient for diagnosis, as it can occur for many reasons in laboring women 6.

Maternal and fetal tachycardia are common—this means a rapid heart rate in either the mother (over 100 bpm) or fetus (over 160 bpm) 1 2 3. These signs suggest a systemic response to infection or inflammation.

Uterine tenderness is another classic symptom—discomfort or pain when the uterus is touched 1 2 3. This can help distinguish chorioamnionitis from other causes of fever during labor.

A foul-smelling vaginal discharge or amniotic fluid is a strong clinical clue, often pointing toward infection 1 2 3.

Leukocytosis, or a raised white blood cell count, supports the diagnosis but is not specific, since it can also occur in normal pregnancy or with other infections 1 2 3.

Diagnostic Challenges

The clinical criteria listed above are not perfectly accurate. Studies show that even when several symptoms are present, only about half of patients truly have microbial infection within the amniotic cavity 1. Therefore, clinicians must combine symptoms with laboratory and sometimes placental pathology data to make a confident diagnosis.

Key Points to Remember

• Not all cases show all symptoms.
• Symptoms can overlap with other labor complications.
• Foul-smelling amniotic fluid and uterine tenderness, especially with fever, are the most predictive of true infection 3.

Types of Chorioamnionitis

Chorioamnionitis is not a single entity, but a spectrum of disease with different underlying mechanisms and clinical presentations. Understanding the types helps guide management and anticipate complications.

Type	Main Features	Diagnostic Basis	Source
Acute	Rapid onset, neutrophil infiltration	Clinical, histologic	4 5
Chronic	Slowly developing, lymphocyte infiltration	Histologic	5
Clinical	Diagnosed by maternal/fetal symptoms	Clinical criteria	1 2
Histological	Diagnosed by placental tissue analysis	Pathology after delivery	4 5 7
Triple I ("Intrauterine Infection or Inflammation or both")	Broader, includes infection and/or inflammation	Clinical + laboratory	6

Table 2: Types of Chorioamnionitis

Acute vs. Chronic Chorioamnionitis

• Acute chorioamnionitis is characterized by a sudden inflammation, typically due to a rapid immune response featuring neutrophil infiltration of the membranes. This is most often linked to bacterial infection, and is associated with preterm birth and significant maternal and neonatal morbidity 4 5.

• Chronic chorioamnionitis develops more gradually, with a predominance of lymphocytes in the placental tissues. It is associated with late preterm births and appears to involve a type of maternal immune rejection of the fetus, rather than classic infection 5.

Clinical vs. Histological Chorioamnionitis

• Clinical chorioamnionitis is diagnosed based on symptoms such as fever, tachycardia, and uterine tenderness during labor 1 2. However, not all clinically diagnosed cases are confirmed by histology or laboratory testing 1.

• Histological chorioamnionitis is identified by examining the placenta after delivery, revealing characteristic patterns of immune cell infiltration 4 5. Interestingly, many cases discovered by histology have no symptoms during labor.

The New Concept: Triple I

To address the limitations of traditional categories, experts recently proposed the term Triple I ("intrauterine inflammation or infection or both"). This broader definition includes cases with inflammation, infection, or both, and highlights that isolated maternal fever does not always equate to chorioamnionitis 6.

Fetal Inflammatory Response

Funisitis and chorionic vasculitis are related conditions representing a fetal immune response. These are detected histologically and are associated with worse neonatal outcomes, including systemic inflammation and risk for long-term complications such as cerebral palsy 4 7.

Causes of Chorioamnionitis

The causes of chorioamnionitis are multifactorial, involving a combination of infectious and non-infectious triggers. Understanding these helps in prevention and individualized care.

Cause	Mechanism/Pathway	Common Microbes or Factors	Source
Ascending Infection	Bacteria travel from vagina/cervix upward	E. coli, Group B Strep, Fusobacterium, Peptostreptococcus, Ureaplasma	2 8 9
Hematogenous Spread	Rare, via maternal bloodstream	Listeria monocytogenes	10
Sterile Inflammation	Non-infectious, cellular stress signals	"Danger signals," cytokine activation	4 10
Maternal Immune Response	Chronic inflammation, immune rejection	Lymphocytic infiltration	5

Table 3: Causes of Chorioamnionitis

Ascending Bacterial Infection

The most common cause of chorioamnionitis is the ascent of bacteria from the lower genital tract into the amniotic cavity 2 8 9. This process is facilitated by:

• Prolonged rupture of membranes
• Frequent vaginal examinations during labor
• Pre-existing infections (e.g., bacterial vaginosis, sexually transmitted infections)

Key implicated organisms include:

• Escherichia coli (E. coli)
• Group B Streptococcus
• Fusobacterium species
• Peptostreptococcus
• Ureaplasma
• Anaerobic streptococci and staphylococci 2 8 9

Severe chorioamnionitis is associated with a higher bacterial load and certain bacterial communities, which can impact newborn size and health 9.

Hematogenous Spread

Rarely, pathogens can reach the placenta via the maternal bloodstream. One classic example is Listeria monocytogenes, but this mechanism is much less common than ascending infection 10.

Sterile Inflammation

Not all cases are infectious. Sterile intraamniotic inflammation can occur when "danger signals" from cellular stress or tissue injury trigger an immune response, even when no microbes are detected 4 10. This highlights the complexity of the syndrome and the importance of distinguishing infection from non-infectious causes.

Maternal Immune Response and Chronic Inflammation

Chronic chorioamnionitis appears to reflect a maternal immune rejection of fetal tissues, rather than infection. The process involves lymphocytic infiltration and is implicated in late preterm birth 5.

Risk Factors

Some factors increase the risk for developing chorioamnionitis:

• Prolonged premature rupture of membranes (PROM)
• Multiple vaginal examinations in labor
• Preterm labor
• Sexually transmitted infections
• Internal fetal monitoring
• Lower socioeconomic status

Treatment of Chorioamnionitis

Prompt and appropriate management of chorioamnionitis is crucial to minimize complications for both mother and baby. Treatment approaches have evolved over time, with growing emphasis on individualized care.

Treatment	Approach/Details	Patient Targeted	Source
Broad-Spectrum Antibiotics	Early administration, often IV	Mother	2 14
Prompt Delivery	Expedite birth after diagnosis	Mother/Baby	14
Neonatal Evaluation	Monitor, test, and treat as needed	Newborn	13 16
Supportive Care	Fluids, antipyretics, management of complications	Mother/Baby	12 14
Antibiotic Prophylaxis	For high-risk PROM, sometimes used	Mother	15

Table 4: Treatment Strategies for Chorioamnionitis

Antibiotic Therapy

Immediate administration of broad-spectrum intravenous antibiotics is the cornerstone of treatment for mothers diagnosed with chorioamnionitis 2 14. Typical regimens include:

• Ampicillin plus gentamicin, with or without clindamycin or metronidazole for anaerobic coverage.
• Antibiotics are continued until delivery, and sometimes postpartum if infection persists.

Delivery Management

Once chorioamnionitis is diagnosed, prompt delivery is recommended to reduce risk of maternal and neonatal complications. However, cesarean section is reserved for standard obstetric indications and not performed solely due to infection 14. Most patients deliver vaginally within 12 hours of diagnosis 14.

Neonatal Care

Babies born to mothers with chorioamnionitis are at increased risk for early-onset sepsis, respiratory distress, and long-term complications 12 7. Management strategies include:

• Close clinical monitoring of the newborn for at least 24 hours 16.
• Laboratory testing (e.g., blood cultures, inflammatory markers) as indicated.
• Empirical antibiotics started if the infant appears unwell or laboratory abnormalities are present 13 16.
• Recent guidelines recommend minimizing unnecessary antibiotic exposure in well-appearing infants, relying more on clinical presentation than routine lab testing 16.

Supportive and Adjunctive Care

• Mothers may require intravenous fluids, antipyretics for fever, and close monitoring for sepsis or other complications 14.
• Neonates may need respiratory support, fluids, or other interventions depending on their condition 12.

Prevention Strategies

• Antibiotic prophylaxis for women with PROM longer than 12 hours has been shown to reduce rates of chorioamnionitis and endometritis 15.
• Reducing unnecessary vaginal examinations and using sterile technique during labor can lower risk.

Evolving Management: Triple I and Individualized Care

The new concept of Triple I emphasizes that treatment should be based on a combination of clinical, laboratory, and sometimes pathologic data 6. Not all cases of maternal fever require the same intervention—individualized care is key to avoid overtreatment and minimize risks.

Conclusion

Chorioamnionitis is a complex, multifaceted syndrome that significantly impacts maternal and neonatal health. Recognizing its symptoms, understanding the various types and causes, and applying evidence-based treatment strategies are essential for optimal outcomes.

Key Takeaways:

• Symptoms: Most commonly include fever, tachycardia (maternal and fetal), uterine tenderness, foul-smelling discharge, and leukocytosis, though not all are always present 1 2 3.
• Types: Acute and chronic, clinical vs. histological, and the broader "Triple I" framework reflect the evolving understanding of this condition 4 5 6.
• Causes: Primarily ascending bacterial infection, but also includes sterile inflammation and immune-mediated mechanisms 2 4 5 8 9 10.
• Treatment: Centers on early antibiotics, timely delivery, and individualized neonatal care—with an increasing focus on preventing unnecessary interventions 2 14 13 16.
• Prevention: Appropriate use of antibiotics in high-risk cases and minimizing invasive procedures during labor help reduce incidence.

By staying informed and proactive, healthcare teams can significantly lessen the risks associated with chorioamnionitis, ensuring better health for mothers and their babies.