Intraamniotic infection, frequently termed chorioamnionitis, signifies an infection triggering inflammation encompassing any combination of the amniotic fluid, placenta, fetus, fetal membranes, or decidua. This condition is commonly observed in both preterm and term pregnancies. Effective recognition and management of intrapartum intraamniotic infection are critical to reducing morbidity and mortality in both mothers and newborns. Prompt maternal care and communication with neonatal healthcare teams are essential for timely evaluation and antibiotic treatment when needed. It’s important to note that chorioamnionitis alone is rarely an indication for cesarean delivery.
Understanding Intraamniotic Infection (Chorioamnionitis)
Intraamniotic infection, or chorioamnionitis, is characterized by infection and subsequent inflammation affecting the amniotic fluid, placenta, fetus, fetal membranes, or decidua. The terminology surrounding this condition is evolving, with some experts suggesting “intraamniotic infection and inflammation” to more comprehensively reflect the disease spectrum (1). However, for clarity and consistency with established guidelines focused on managing suspected or confirmed infection, the term intraamniotic infection remains widely used.
This infection is often polymicrobial, involving both aerobic and anaerobic bacteria, typically originating from the vaginal flora (2). The primary route of infection is ascending bacterial invasion from the lower genital tract into the amniotic cavity, which is usually sterile. Less frequently, intraamniotic infection can occur following invasive procedures like amniocentesis or chorionic villus sampling, or via hematogenous spread from maternal systemic infections, such as Listeria monocytogenes. Clinically apparent intraamniotic infection complicates approximately 2–5% of term deliveries (3, 4). Recent data indicates a potential increase in the risk of intraamniotic infection and neonatal infection beyond 40 weeks of gestation (3, 4, 5).
Neonatal and Maternal Risks Associated with Chorioamnionitis
Intraamniotic infection poses significant risks to newborns, including acute conditions such as neonatal pneumonia, meningitis, sepsis, and even death (3). However, the implementation of intrapartum antibiotic treatment, driven by maternal Group B Streptococcus colonization status or evolving signs of intraamniotic infection, has dramatically reduced group B streptococcal-specific neonatal sepsis cases by nearly tenfold (6, 7, 8). Reductions in other non-group B streptococcal neonatal infections have also been observed (9, 10, 11). Maternal intrapartum antibiotic administration has proven protective against neonatal sepsis in various risk models (5, 12).
Beyond acute neonatal morbidities, chorioamnionitis is linked to long-term infant complications such as bronchopulmonary dysplasia and cerebral palsy (13, 14), potentially due to inflammation itself. A meta-analysis of 15 studies highlighted a significantly elevated relative risk of cerebral palsy in predominantly premature infants exposed to histologic chorioamnionitis (OR, 1.8; 95% CI, 1.17–2.89) or clinical chorioamnionitis (OR, 2.4; 95% CI, 1.52–3.84) (13). Despite this increased relative risk, the overall absolute risk of cerebral palsy remains low (approximately 2 per 1,000 live births) (15).
Maternal health is also at risk from intraamniotic infection, with potential complications including dysfunctional labor requiring more interventions, postpartum uterine atony with hemorrhage, endometritis, peritonitis, sepsis, adult respiratory distress syndrome, and, in rare instances, death (16, 17).
Risk Factors for Intraamniotic Infection
Several obstetric risk factors for intraamniotic infection at term have been identified. These include low parity, frequent digital cervical examinations, use of internal uterine and fetal monitors, meconium-stained amniotic fluid, and the presence of certain genital tract pathogens like Group B Streptococcus and sexually transmitted infections (3, 18, 19, 20). It’s important to consider that many of these factors are also associated with prolonged labor and membrane rupture, and may not be independently linked to intraamniotic infection. For instance, a study analyzing over 2,000 deliveries found that women who developed intrapartum fever had undergone more digital cervical exams than those who did not (21). However, this correlation was not significant after adjusting for spontaneous labor, Bishop score, and membrane rupture upon admission.
Maternal intraamniotic infection demonstrates reasonable sensitivity but lacks specificity in diagnosing neonatal sepsis, especially in preterm infants. Risk models for predicting neonatal sepsis in term and late-preterm infants incorporate factors like gestational age, duration of membrane rupture, maximum maternal intrapartum temperature, Group B Streptococcus colonization, and the type and timing of intrapartum antibiotics (5, 12, 22). While these models don’t alter intrapartum maternal management, they emphasize the importance of communication with pediatric care providers and thorough maternal medical record documentation.
Diagnostic Criteria for Chorioamnionitis: Suspected vs. Confirmed
Objective diagnosis of intraamniotic infection can be achieved through amniotic fluid culture, Gram stain, and biochemical analysis. However, in most term laboring women, diagnosis relies primarily on clinical criteria. Experts have categorized intraamniotic infection into three groups: isolated maternal fever, suspected intraamniotic infection, and confirmed intraamniotic infection (1). These distinctions are based on clinical and laboratory/pathologic findings and provide standardized temperature criteria for intrapartum fever diagnosis.
Isolated maternal fever is defined as a single oral temperature of 39.0°C or higher, or a sustained oral temperature between 38.0–38.9°C for at least 30 minutes.
Suspected intraamniotic infection is diagnosed based on maternal intrapartum fever accompanied by one or more of the following: maternal leukocytosis, purulent cervical discharge, or fetal tachycardia.
Confirmed intraamniotic infection is established by positive amniotic fluid test results (Gram stain, glucose level, or culture results indicative of infection) or placental pathology showing histologic evidence of placental infection or inflammation. In term labor, confirmed diagnosis often occurs postpartum via placental histopathology. The practical distinction between suspected and confirmed intraamniotic infection is most relevant in research settings, as management for laboring patients is similar in both scenarios until more readily available intrapartum diagnostic tools emerge. While expert guidelines initially categorized patients with a temperature of 39°C or greater without other risk factors as isolated maternal fever, it is clinically prudent to include these patients within the suspected intraamniotic infection group unless an alternative cause is evident. This approach prioritizes sensitivity, acknowledging that significantly elevated maternal temperatures are more likely indicative of infection, while lower, transient fevers might be spurious or related to non-infectious factors like dehydration or epidural analgesia (23, 24, 25).
Management Strategies for Suspected or Confirmed Chorioamnionitis
Intrapartum antibiotic therapy for intraamniotic infection is proven to reduce neonatal bacteremia, pneumonia, and sepsis rates (26). Risk models for neonatal sepsis also demonstrate the beneficial impact of intrapartum antibiotics on culture-confirmed neonatal infection risk (5, 12). Furthermore, intrapartum antibiotics reduce maternal febrile morbidity and hospital stay duration. Therefore, unless clear contraindications exist, intrapartum antibiotics are recommended whenever intraamniotic infection is suspected or confirmed (26). Antipyretics should be administered alongside antibiotics. Given the association between intraamniotic infection and dysfunctional labor (3, 16, 17, 27), ensuring proper labor progression is crucial. Augmentation of protracted labor in women with intraamniotic infection is generally advisable, provided no contraindications are present. However, intraamniotic infection itself is not an indication for immediate delivery, and the delivery route should be determined by standard obstetric indications. Cesarean delivery is rarely, if ever, necessary solely due to intraamniotic infection.
Addressing Isolated Maternal Fever
Isolated maternal fever, defined as a temperature between 38.0°C and 38.9°C without other clinical signs of intraamniotic infection, with or without persistent elevation, is a common clinical scenario. Despite the absence of additional criteria, clinicians often opt to treat for intraamniotic infection due to the potential risks. Limited data exists to definitively guide management of isolated intrapartum fever in the absence of other suggestive signs. Isolated intrapartum fever, regardless of its cause, has been associated with adverse short-term and long-term neonatal outcomes (28, 29, 30). The exact mechanism remains unclear, though fetal hyperthermia and related metabolic changes are hypothesized to exacerbate the negative effects of tissue hypoxia. Prospective, randomized controlled studies are needed to optimize the management of isolated intrapartum fever. Currently, given the potential benefits for both mother and newborn, antibiotics should be considered for isolated maternal fever unless another source is identified and documented. This approach may increase the detection and diagnosis of intraamniotic infection, influencing subsequent newborn management. Regardless of antibiotic initiation, maternal intrapartum fever should always be communicated to the neonatal care team. Current pediatric guidelines increasingly rely on a broader assessment of risk factors and newborn clinical status, rather than solely on suspected intraamniotic infection diagnosis, to guide neonatal management.
Postpartum Management Considerations
Intrapartum antibiotics administered for suspected or confirmed intraamniotic infection should not automatically continue postpartum. Postpartum antibiotic continuation should be guided by risk factors for postpartum endometritis (31, 32, 33, 34). Women with vaginal deliveries are less likely to develop endometritis and may not require postpartum antibiotics (32). For cesarean deliveries, at least one additional antibiotic dose post-delivery is recommended. However, maternal risk factors such as bacteremia or persistent postpartum fever may necessitate extended antibiotic therapy, and influence the duration of treatment for both vaginal and cesarean deliveries.
Common antibiotic regimens for suspected intraamniotic infection are detailed in Table 1. Consultation with local microbiology laboratories and infectious disease experts is recommended to determine optimal regimens based on local antibiotic resistance patterns.
Table 1: Common Antibiotic Regimens for Intrapartum Management of Suspected Intraamniotic Infection.
Neonatal Implications of Chorioamnionitis Diagnosis
Guidelines from the Centers for Disease Control and Prevention and the American Academy of Pediatrics outline neonatal infection risk assessment (7, 35, 36, 37). These guidelines recommend laboratory evaluations and empiric antibiotic therapy for all newborns delivered to mothers with suspected or confirmed intraamniotic infection. Current recommendations are undergoing re-evaluation (1, 38). Emerging data on neonatal microbiome development and the impact of early antibiotic exposure suggest that antibiotic therapy is not without potential drawbacks (39, 40, 41, 42, 43, 44, 45, 46). Risk assessment models and a greater emphasis on clinical observation may safely reduce the number of well-appearing term newborns receiving empiric antibiotics (5, 12, 22). In all cases of maternal isolated fever and suspected or confirmed intraamniotic infection, communication with neonatal caregivers at birth is paramount. Regardless of evolving guidelines and local practice variations, these infants require heightened clinical surveillance for signs of developing infection.
Conclusion: Optimizing Chorioamnionitis Diagnosis and Management
Intraamniotic infection remains a prevalent condition in both preterm and term pregnancies. Early recognition and adherence to treatment recommendations are crucial for minimizing morbidity and mortality in mothers and newborns. Timely maternal management, coupled with effective communication with neonatal healthcare providers, facilitates appropriate evaluation and judicious empiric antibiotic use when indicated. Chorioamnionitis alone is rarely a reason for cesarean delivery.
References
[List of references as in the original article]
Disclaimer: This information is intended as an educational resource for clinicians and should not be considered medical advice or a standard of care. Clinical judgment and individual patient needs should always guide medical decisions.
