RCOG Diagnostic Criteria for Chorioamnionitis
According to the Royal College of Obstetricians and Gynaecologists (RCOG), chorioamnionitis should be diagnosed using a multimodal approach that combines clinical assessment, maternal inflammatory markers, and fetal monitoring—no single parameter should be used in isolation. 1
Core Diagnostic Components
The RCOG mandates the following integrated assessment for diagnosing chorioamnionitis in women with preterm prelabour rupture of membranes (PPROM):
Clinical Assessment
- Record maternal vital signs including pulse, blood pressure, respiratory rate, and temperature on an obstetric early warning chart 1
- Assess for clinical symptoms: lower abdominal pain, abnormal vaginal discharge, fever, malaise, and reduced fetal movements 1
- Document uterine tenderness and character of any vaginal discharge 1
Laboratory Parameters
- Measure C-reactive protein (CRP): A threshold of ≥8 mg/L yields specificity of 63.3%–77.1% for chorioamnionitis, though sensitivity is only 68.7% 2
- Obtain white blood cell (WBC) count: Recognize that WBC rises 24 hours after corticosteroid administration and returns to baseline approximately 3 days later 1, 2
- CRP results should be reported to one decimal place in mg/L using high-sensitivity assays 2
Fetal Assessment
- Perform fetal heart rate monitoring using cardiotocography to detect fetal tachycardia as a sign of infection 1
- Continuous fetal heart rate monitoring should be integrated with maternal clinical and laboratory findings 3
Critical Interpretation Guidelines
When laboratory results and clinical assessment are discordant, continue observation and repeat testing rather than making immediate management decisions. 2 This is a crucial pitfall to avoid—an isolated elevated CRP without accompanying clinical signs should not trigger immediate delivery 4, 3.
Monitoring Protocols
For inpatient management:
- Record vital signs at regular intervals on obstetric early-warning charts 2
- Perform ongoing clinical surveillance for new symptoms 2
- Measure CRP and WBC as components of routine infection surveillance, recognizing that serial trends are more informative than isolated values 2
For outpatient management:
- Schedule reviews once or twice weekly in day-care, maternity triage, or antenatal clinics 1, 2
- At each visit, obtain blood tests (CRP and WBC), document clinical findings, and perform fetal heart rate monitoring 2
- Advise immediate hospital attendance if concerning symptoms develop 1
Important Caveats
The RCOG criteria differ substantially from traditional Gibbs criteria used at term, which require fever as a prerequisite. Research demonstrates that conventional clinical criteria (Gibbs, Lencki) have poor sensitivity (only 15.4%) for detecting intraamniotic infection in preterm pregnancies 5. The RCOG approach addresses this limitation by emphasizing the combination of multiple parameters rather than relying on fever alone.
Corticosteroid interference must be considered: WBC counts are transiently elevated by antenatal steroids, whereas CRP levels remain relatively unaffected, making CRP a more reliable marker during steroid therapy 2.
If CRP exceeds 10 mg/L, repeat testing and focused evaluation for infection sources are recommended 2, though this threshold alone does not mandate delivery without supporting clinical evidence.