Chorioamnionitis

Chorioamnionitis is an infection of the fetal membranes and amniotic fluid that can lead to serious maternal and neonatal complications. It often occurs during labor or following premature rupture of membranes. Early recognition and treatment are essential to prevent adverse outcomes.

Introduction

Chorioamnionitis, also known as intra-amniotic infection, involves inflammation of the chorion, amnion, and amniotic fluid due to microbial invasion. It is a significant cause of maternal fever, preterm labor, and neonatal sepsis. Prompt diagnosis and management are crucial for improving maternal and fetal outcomes.

Definition and Overview

Definition of Chorioamnionitis

Chorioamnionitis is defined as an infection of the fetal membranes, amniotic fluid, placenta, and sometimes the decidua. It results from bacterial, viral, or fungal invasion, typically ascending from the lower genital tract. The condition can be classified as clinical or histological based on presentation and diagnostic criteria.

Historical Background

The recognition of chorioamnionitis dates back to the early 20th century when maternal fever and fetal complications were linked to intrauterine infections. Over the years, advances in microbiology, obstetrics, and neonatal care have improved the understanding, diagnosis, and treatment of this condition.

Classification

Chorioamnionitis can be classified into two main categories:

• Clinical Chorioamnionitis: Diagnosed based on maternal fever and other clinical signs such as uterine tenderness, maternal or fetal tachycardia, and purulent amniotic fluid.
• Histological Chorioamnionitis: Identified by microscopic examination of the placenta and membranes showing inflammatory cell infiltration, often without overt clinical symptoms.

Etiology and Risk Factors

Microbial Causes

• Bacterial: The most common pathogens include Group B Streptococcus, Escherichia coli, Ureaplasma species, Mycoplasma hominis, and anaerobic bacteria.
• Viral and Fungal Causes: Less common, but infections with herpes simplex virus, cytomegalovirus, or Candida species can occasionally contribute.

Maternal Risk Factors

• Prolonged rupture of membranes (>18 hours)
• Multiple vaginal examinations during labor
• Preterm labor or preterm premature rupture of membranes
• Intrauterine procedures such as amniocentesis or cervical cerclage

Obstetric Risk Factors

• Nulliparity
• Prolonged labor
• Presence of meconium-stained amniotic fluid

Pathophysiology

Mechanism of Infection

Chorioamnionitis typically develops via an ascending infection from the lower genital tract. Microorganisms invade the amniotic cavity, leading to colonization of the fetal membranes, amniotic fluid, and placenta. Less commonly, hematogenous spread from maternal bloodstream infections can occur.

Inflammatory Response

The maternal immune system responds with an influx of neutrophils and the release of pro-inflammatory cytokines such as interleukin-6 and tumor necrosis factor-alpha. This inflammatory cascade contributes to uterine contractions, membrane weakening, and systemic maternal symptoms.

Effects on Maternal and Fetal Systems

In the mother, chorioamnionitis can lead to fever, tachycardia, and sepsis. In the fetus, inflammation can cause fetal tachycardia, preterm labor, and neonatal complications such as sepsis, respiratory distress, and long-term neurological impairment.

Clinical Presentation

Maternal Symptoms

• Fever, typically >38°C
• Uterine tenderness on palpation
• Foul-smelling or purulent amniotic fluid
• Maternal tachycardia (>100 bpm)
• Chills and general malaise

Fetal and Neonatal Signs

• Fetal tachycardia (>160 bpm)
• Reduced or abnormal fetal movements
• Signs of neonatal sepsis, including respiratory distress, temperature instability, or hypotension
• Long-term neurological complications in severe or untreated cases

Diagnostic Evaluation

Laboratory Investigations

• Maternal blood tests: Complete blood count showing leukocytosis, elevated C-reactive protein (CRP)
• Blood cultures to identify systemic infection
• Amniotic fluid analysis: Gram stain, culture, glucose concentration, and interleukin-6 levels

Imaging Studies

• Ultrasound: To assess amniotic fluid volume, placental abnormalities, or fetal well-being

Clinical Criteria

Diagnosis is often based on maternal fever plus one or more of the following: uterine tenderness, maternal or fetal tachycardia, and purulent amniotic fluid. Clinical assessment remains the primary tool for timely diagnosis and management.

Management and Treatment

Antibiotic Therapy

• First-line regimens typically include intravenous ampicillin combined with gentamicin for broad-spectrum coverage
• Alternative regimens for patients with allergies or resistant organisms may include clindamycin or vancomycin in combination with gentamicin
• Duration of therapy is generally continued until delivery and may be extended postpartum if maternal infection persists

Obstetric Management

• Induction of labor is often indicated in term pregnancies to reduce the risk of maternal and fetal complications
• Cesarean delivery may be required for obstetric indications or if there is non-reassuring fetal status

Supportive Care

• Maternal monitoring includes frequent assessment of vital signs, hydration status, and laboratory parameters
• Fetal monitoring is essential to detect tachycardia, distress, or other signs of compromise

Complications

Maternal Complications

• Sepsis and septic shock in severe or untreated cases
• Postpartum hemorrhage due to uterine atony or infection
• Endometritis and delayed wound healing

Fetal and Neonatal Complications

• Neonatal sepsis and systemic infections
• Preterm birth and associated complications such as respiratory distress syndrome
• Long-term neurological impairments, including cerebral palsy, in severe cases

Prevention

Maternal Screening and Prophylaxis

• Routine screening for Group B Streptococcus (GBS) at 35–37 weeks of gestation
• Intrapartum antibiotic prophylaxis for GBS-positive mothers or those with risk factors such as prolonged rupture of membranes

Obstetric Practices

• Minimizing the number of vaginal examinations during labor
• Timely management of prolonged labor and rupture of membranes
• Strict aseptic technique during intrauterine procedures such as amniocentesis

Prognosis

Maternal Prognosis

With prompt diagnosis and appropriate antibiotic therapy, maternal outcomes are generally favorable. Early intervention reduces the risk of sepsis, postpartum complications, and long-term morbidity.

Neonatal Prognosis

Neonatal outcomes depend on gestational age at delivery, severity of infection, and timeliness of treatment. Early antibiotic administration and supportive care improve survival and reduce the risk of long-term complications such as neurological impairment.

Recent Advances and Research

Novel Diagnostic Biomarkers

Recent studies have identified biomarkers such as interleukin-6, interleukin-8, and procalcitonin in maternal serum or amniotic fluid, which can improve early detection and risk stratification of chorioamnionitis.

Antibiotic Stewardship and Resistance Patterns

Research is ongoing to optimize antibiotic regimens to prevent resistance while ensuring effective maternal and neonatal treatment. Strategies include targeted therapy based on culture results and minimizing unnecessary broad-spectrum antibiotic use.

Preventive Strategies and Vaccines

Emerging preventive approaches focus on maternal immunization against pathogens such as Group B Streptococcus and developing vaccines that reduce the incidence of intra-amniotic infection, potentially decreasing the risk of preterm birth and neonatal sepsis.

References

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