Chorioamnionitis: A Comprehensive Review

Introduction

Chorioamnionitis is a clinically significant infection of the fetal membranes (chorion and amnion), amniotic fluid, and placenta that primarily occurs during pregnancy. It is a major cause of maternal and neonatal morbidity and mortality worldwide, particularly in the context of preterm labour and delivery. The condition, also known as intra-amniotic infection (IAI), is a common complication in obstetric practice and presents unique diagnostic and management challenges.

Definition

Chorioamnionitis refers to an acute inflammatory condition of the fetal membranes (amnion and chorion) and amniotic fluid, usually due to bacterial infection. While the term is often used interchangeably with intra-amniotic infection, chorioamnionitis may also encompass sterile inflammation of the membranes. The diagnosis is typically clinical, based on maternal fever and associated features, but may also be confirmed by laboratory and histopathological findings.

Epidemiology and Significance

The incidence of clinical chorioamnionitis varies depending on population, clinical setting, and diagnostic criteria but is estimated to occur in 1–5% of all term deliveries and 5–12% of preterm births. Subclinical infection is considerably more common, with histological evidence found in up to 20% of preterm deliveries. Chorioamnionitis is associated with adverse maternal outcomes such as postpartum endometritis, sepsis, and increased rates of caesarean delivery, as well as significant neonatal complications including early-onset sepsis, pneumonia, and long-term neurodevelopmental impairment. Its recognition and timely management are therefore critical in obstetric care.

Etiology and Risk Factors

Causative Organisms

Chorioamnionitis is most commonly a result of ascending polymicrobial bacterial infection from the lower genital tract. The major pathogens implicated include:

• Ureaplasma urealyticum and Mycoplasma hominis: These are the most frequently isolated organisms in chorioamnionitis.
• Gardnerella vaginalis
• Group B Streptococcus (GBS)
• Escherichia coli
• Anaerobic bacteria such as Bacteroides species
• Other organisms including Streptococcus species, Staphylococcus aureus, and occasionally, viruses or fungi

In rare cases, infection may arise from haematogenous spread, especially with organisms such as Listeria monocytogenes.

Maternal and Fetal Risk Factors

Several factors increase the risk of developing chorioamnionitis:

• Prolonged rupture of membranes (PROM): The risk rises significantly when the duration of membrane rupture exceeds 18 hours.
• Preterm labour: Both a cause and consequence of intra-amniotic infection.
• Multiple vaginal examinations: Increased frequency during labour raises the risk of ascending infection.
• Internal fetal monitoring: Use of scalp electrodes or intrauterine pressure catheters can introduce pathogens.
• Bacterial vaginosis: Disruption of normal vaginal flora predisposes to infection.
• Cervical cerclage: The presence of a foreign body may facilitate infection.
• Young maternal age, nulliparity, low socioeconomic status, and poor antenatal care: These social determinants are linked to higher incidence rates.
• Sexually transmitted infections (STIs): History of STIs increases the risk.
• Immunosuppression: Maternal conditions such as HIV/AIDS or use of immunosuppressive drugs.

Fetal risk factors are largely secondary to maternal and obstetric factors, but include pre-existing fetal compromise or immunodeficiency.

Pathophysiology

The pathogenesis of chorioamnionitis involves a complex interplay of microbial invasion, host immune response, and inflammatory mediators.

Mechanisms of Infection

The most common pathway is the ascending route, where organisms from the vagina and cervix colonise the decidua, then penetrate the chorion and amnion, eventually contaminating the amniotic fluid. Less commonly, infection may result from haematogenous spread, direct inoculation during invasive procedures, or retrograde infection from the peritoneal cavity.

Inflammatory Response

Once pathogens reach the amniotic cavity, they trigger an acute inflammatory response characterised by the release of pro-inflammatory cytokines (such as interleukins and tumour necrosis factor-alpha), chemokines, and prostaglandins. These mediators recruit neutrophils and other immune cells to the site of infection, resulting in tissue damage, increased production of amniotic fluid, and stimulation of uterine contractions. The inflammatory process may extend to involve the fetus, leading to a fetal inflammatory response syndrome (FIRS), which is associated with adverse neonatal outcomes.

Clinical Features

The presentation of chorioamnionitis can vary from subclinical (asymptomatic) to fulminant infection with maternal and fetal compromise.

Maternal Signs and Symptoms

The classic clinical features include:

• Maternal fever: Temperature >38°C (100.4°F) is the hallmark of chorioamnionitis.
• Tachycardia: Maternal heart rate >100 beats per minute.
• Uterine tenderness: Pain on palpation of the uterus, not explained by labour alone.
• Foul-smelling or purulent amniotic fluid: Noted on examination or rupture of membranes.
• Leukocytosis: Elevated maternal white blood cell count (>15,000/mm³), though this may also occur physiologically during pregnancy.
• Other symptoms: Chills, malaise, and lower abdominal pain may be present.

Fetal Signs and Symptoms

Fetal involvement is suggested by:

• Fetal tachycardia: Baseline heart rate >160 beats per minute.
• Fetal distress: Non-reassuring fetal heart rate patterns, reduced variability, or late decelerations.
• Meconium-stained amniotic fluid: May indicate fetal compromise.

In severe cases, fetal sepsis or demise may occur.

Diagnosis

Diagnosis of chorioamnionitis is primarily clinical but is supported by laboratory and, in selected cases, imaging findings.

Clinical Criteria

The diagnosis is typically made in the presence of maternal fever (≥38°C) plus two or more of the following:

• Maternal tachycardia (>100 bpm)
• Fetal tachycardia (>160 bpm)
• Uterine tenderness
• Foul or purulent amniotic fluid
• Maternal leukocytosis (>15,000/mm³)

The American College of Obstetricians and Gynecologists (ACOG) recommends using the term “suspected intra-amniotic infection” for patients with clinical features, and “confirmed intra-amniotic infection” when there is laboratory or microbiological evidence.

Laboratory Tests

Laboratory investigations can aid in diagnosis and exclude other causes:

• Complete blood count (CBC): Leukocytosis is supportive but non-specific.
• C-reactive protein (CRP) and procalcitonin: Elevated in infection but limited specificity.
• Blood cultures: To detect maternal bacteraemia, though positive in only a minority of cases.
• Amniotic fluid analysis (via amniocentesis): May show elevated white blood cell count, low glucose, high lactate dehydrogenase (LDH), and positive Gram stain or culture. Amniocentesis is reserved for equivocal cases due to procedural risks.

Imaging

Imaging has a limited role in acute diagnosis:

• Ultrasound: May show increased echogenicity of amniotic fluid or debris, but findings are non-specific.
• Magnetic Resonance Imaging (MRI): Rarely used, but can assess for placental or fetal involvement in complex cases.

Differential Diagnosis

The clinical picture of chorioamnionitis can mimic other obstetric and non-obstetric conditions, including:

• Labour with physiological fever
• Preeclampsia with HELLP syndrome
• Urinary tract infection or pyelonephritis
• Appendicitis
• Influenza or other systemic infections

A thorough assessment is essential to exclude these alternative diagnoses.

Management

The management of chorioamnionitis involves prompt initiation of broad-spectrum antibiotics, consideration of delivery timing, and supportive care for both mother and fetus.

Medical and Obstetric Interventions

The mainstays of treatment are:

• Antibiotic therapy: Empirical broad-spectrum antibiotics should be started as soon as chorioamnionitis is suspected. The most commonly used regimen is intravenous ampicillin and gentamicin, with clindamycin or metronidazole added for anaerobic coverage in cases of caesarean delivery. Therapy should continue until the patient is afebrile for 24–48 hours.
• Supportive care: Includes antipyretics for fever, intravenous fluids for hydration, and monitoring of maternal and fetal status.
• Delivery: The definitive treatment for chorioamnionitis is delivery of the fetus and placenta. The timing and mode of delivery depend on gestational age, maternal and fetal condition, and cervical status. Vaginal delivery is preferred unless there are obstetric indications for caesarean section.
• Neonatal care: All infants born to mothers with chorioamnionitis should be evaluated for sepsis and managed accordingly with antibiotics and supportive therapy.

Antibiotic Regimens

Commonly used antibiotics include:

• Ampicillin 2 g IV every 6 hours plus Gentamicin 5 mg/kg IV every 24 hours
• For penicillin-allergic patients: Clindamycin plus Gentamicin
• For caesarean delivery: Add Clindamycin 900 mg IV every 8 hours or Metronidazole 500 mg IV every 8 hours to cover anaerobes

Antibiotics are generally continued until the mother is afebrile for at least 24 hours postpartum.

Delivery Considerations

• Vaginal delivery: Preferred route if there are no contraindications, as caesarean delivery in the presence of infection increases maternal morbidity.
• Caesarean section: Reserved for standard obstetric indications (e.g., fetal distress, failure to progress). Prophylactic antibiotics are essential.
• Gestational age: In preterm pregnancies, the risks and benefits of immediate delivery versus expectant management must be carefully weighed. However, ongoing infection generally mandates delivery.

Complications

Chorioamnionitis is associated with significant maternal, fetal, and neonatal complications.

Maternal Complications

• Postpartum endometritis: Infection of the uterine lining after delivery.
• Wound infection and pelvic abscess: Especially after caesarean section.
• Sepsis and septic shock: Potentially life-threatening systemic infection.
• Disseminated intravascular coagulation (DIC): A severe complication with high morbidity.
• Increased risk of postpartum haemorrhage
• Longer hospital stay and recovery period

Fetal and Neonatal Complications

• Preterm birth: Infection is a leading cause of spontaneous preterm labour and preterm premature rupture of membranes (PPROM).
• Early-onset neonatal sepsis: Life-threatening infection in the newborn, often requiring intensive care.
• Pneumonia and meningitis: Serious infections with long-term consequences.
• Perinatal asphyxia and hypoxic-ischemic encephalopathy: Due to impaired placental function.
• Neonatal death
• Long-term neurodevelopmental impairment: Increased risk of cerebral palsy, cognitive and behavioural problems, especially in preterm infants.

Prevention

Prevention of chorioamnionitis focuses on reducing risk factors and early identification of possible infection.

Screening and Prophylactic Measures

• Antenatal screening for genitourinary infections: Identifying and treating bacterial vaginosis, GBS colonisation, and urinary tract infections during pregnancy.
• Minimising vaginal examinations: Limit the number of digital examinations during labour, especially after membrane rupture.
• Avoiding unnecessary invasive procedures: Such as internal fetal monitoring and amniocentesis unless clearly indicated.
• Prompt induction of labour: In women with PROM, especially at term, to reduce the duration of membrane rupture.
• Use of prophylactic antibiotics: In cases of preterm PROM, GBS colonisation, or prolonged rupture of membranes.
• Optimising antenatal care: Ensuring regular follow-up, health education, and early detection of infections.

Prognosis

The prognosis of chorioamnionitis depends on the timing of diagnosis, adequacy of treatment, and presence of complications.

Short-term Outcomes

With timely and appropriate management, most mothers recover without long-term sequelae. However, there is a higher risk of postpartum infections and, rarely, severe complications such as sepsis or DIC.

Long-term Outcomes

For the neonate, the risk of adverse outcomes is closely linked to gestational age at delivery and severity of infection. Preterm infants are especially vulnerable to neurodevelopmental impairment, cerebral palsy, and chronic lung disease. Long-term follow-up is recommended for infants exposed to intrauterine infection.

Nursing Care of Patients with Chorioamnionitis

Goals of Nursing Care

The primary goals in the nursing care of chorioamnionitis are:

• Early recognition and reporting of signs and symptoms
• Prompt initiation of prescribed antibiotic therapy
• Monitoring and supporting maternal and fetal wellbeing
• Minimizing complications for parent and newborn
• Providing education and emotional support

Assessment and Monitoring

Maternal Assessment:

• Vital signs: Monitor temperature, heart rate, respiratory rate, and blood pressure at least every 2 hours, more frequently if clinically indicated.
• Uterine assessment: Palpate for tenderness or rigidity.
• Amniotic fluid: Observe for color, odor, and consistency during rupture or as fluid drains.
• Monitor for signs of progression to sepsis: hypotension, tachypnea, altered mental status.
• Laboratory data: Monitor white blood cell counts, blood cultures, and other relevant labs as ordered.

Fetal Assessment:

• Continuous fetal heart rate monitoring to detect tachycardia or signs of distress.
• Observation for meconium-stained amniotic fluid, which may indicate fetal compromise.
• Assessment of fetal movements as reported by the birthing parent.

Medical Management and Nursing Interventions

Antibiotic Therapy:

• Administer broad-spectrum intravenous antibiotics as ordered, typically including ampicillin and gentamicin, and clindamycin or metronidazole if cesarean delivery is anticipated or performed.
• Monitor for allergic reactions and ensure medication is administered on schedule.

Supportive Management:

• Administer antipyretics (e.g., acetaminophen) for fever as prescribed.
• Maintain adequate hydration through oral or intravenous fluids to support maternal and fetal circulation and prevent hypotension.
• Monitor intake and output, reporting oliguria or signs of fluid overload.
• Provide oxygen therapy if maternal or fetal hypoxia is suspected.

Labor and Delivery:

• Collaborate closely with the physician or midwife regarding timing and mode of delivery. Prompt delivery may be indicated if infection is severe or labor is not progressing.
• Prepare for possible emergency cesarean section if fetal distress or maternal decompensation occurs.
• Minimize the number of vaginal examinations to reduce the risk of further infection.
• Support the birthing parent with pain management and comfort measures.

Postpartum Care

Chorioamnionitis increases the risk of postpartum complications such as endometritis, wound infection, and sepsis.

• Continue antibiotics as prescribed until the parent is afebrile for at least 24-48 hours.
• Monitor for postpartum hemorrhage, as infection can impair uterine contractility.
• Assess for signs of wound infection (if cesarean) or perineal infection (if vaginal delivery).
• Provide emotional support, especially if birth experience was traumatic or resulted in neonatal complications.
• Educate on signs of infection, the importance of medication adherence, and when to seek immediate care after discharge.

Newborn Care

Neonates born to parents with chorioamnionitis are at increased risk for early-onset sepsis, pneumonia, meningitis, and other complications.

• Ensure immediate and thorough assessment of the newborn by a pediatrician or neonatologist.
• Monitor for respiratory distress, temperature instability, poor feeding, lethargy, or irritability.
• Obtain blood cultures and initiate empiric antibiotics as per hospital protocol until sepsis is ruled out.
• Support thermoregulation and glucose stability.
• Educate parents on signs of neonatal infection and the need for follow-up care.

Patient and Family Education

Education is a vital component in the nursing care of chorioamnionitis. Nurses should provide clear, empathetic communication regarding:

• The nature of the infection and its potential impact on both parent and baby
• Importance of completing the full course of antibiotics
• Signs and symptoms of worsening infection or postpartum complications
• When to seek urgent medical attention
• Emotional support resources, especially if the birth experience was traumatic

Prevention Strategies

While not all cases can be prevented, certain measures can reduce the risk of chorioamnionitis:

• Minimize the frequency of vaginal examinations during labor
• Adhere strictly to aseptic technique during procedures
• Treat urinary tract and vaginal infections promptly during pregnancy
• Monitor for and address prolonged rupture of membranes
• Educate pregnant patients on the importance of prenatal care and reporting symptoms such as fever, foul-smelling vaginal discharge, or reduced fetal movement

Documentation and Communication

Meticulous documentation is critical for continuity of care and medico-legal protection. Nurses should record:

• All assessments and vital signs, especially temperature and fetal heart rate trends
• Administration of medications, fluids, and any reactions
• Patient education provided and the response
• Communication with the healthcare team regarding changes in status
• Any interventions performed and their outcomes

Interdisciplinary Collaboration

Effective care for patients with chorioamnionitis requires collaboration among obstetricians, midwives, pediatricians, neonatologists, infectious disease specialists, and nursing staff. Regular team huddles, clear communication, and shared care plans enhance patient outcomes and safety.

Emotional and Psychological Support

A diagnosis of chorioamnionitis can be distressing. Nurses must assess for anxiety, fear, or feelings of guilt, and offer supportive counseling. Referrals to mental health professionals or social work may be appropriate, particularly in cases involving preterm birth, neonatal complications, or prolonged hospitalization.

Complications to Monitor

Nurses should be vigilant for the following complications:

• Sepsis (parent and newborn)
• Endometritis
• Postpartum hemorrhage
• Neonatal respiratory distress
• Preterm birth and its consequences

REFERENCES

1. Tita AT, Andrews WW. Diagnosis and management of clinical chorioamnionitis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008318/. Clin Perinatol. 2010 Jun;37(2):339-54.
2. Fowler JR, Simon LV. Chorioamnionitis. 2023 Sep 4. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. PMID: 30335284.
3. The American College of Obstetricians and Gynecologists. Intrapartum Management of Intraamniotic Infection. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/08/intrapartum-management-of-intraamniotic-infection.
4. March of Dimes. Maternal Death and Pregnancy-Related Death. https://www.marchofdimes.org/complications/pregnancy-related-death-maternal-death-and-maternal-mortality.aspx.
5. Johnson CT, Farzin A, Burd I. Current management and long-term outcomes following chorioamnionitis. Obstet Gynecol Clin North Am. 2014 Dec;41(4):649-69. doi: 10.1016/j.ogc.2014.08.007. Epub 2014 Nov 20. PMID: 25454996; PMCID: PMC4254434.
6. Merck Manual. Intra-amniotic Infection. https://www.merckmanuals.com/professional/gynecology-and-obstetrics/abnormalities-of-pregnancy/intra-amniotic-infection.
7. Conde-Agudelo A, Romero R, Jung EJ, Garcia Sánchez ÁJ. Management of clinical chorioamnionitis: an evidence-based approach. Am J Obstet Gynecol. 2020 Dec;223(6):848-869. doi: 10.1016/j.ajog.2020.09.044. Epub 2020 Sep 29. PMID: 33007269; PMCID: PMC8315154.

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