Triple I (intra-amniotic infection)

Definition

Term

• "Triple I" stands for intrauterine inflammation/infection.
• The term replaced the term “chorioamnionitis”.
• The working diagnosis rests on maternal fever plus one additional criterion.

• Triple I stands for intra-amniotic infection or inflammation or both; the term was proposed by an NICHD expert panel to replace the clinical diagnosis of chorioamnionitis.

Classification

• Clinical criteria are maternal fever together with further signs such as maternal tachycardia above 100 bpm, fetal tachycardia above 160 bpm, uterine tenderness, purulent or foul-smelling amniotic fluid or leucocytosis above 15,000/mm³; fever thresholds differ between definitions.

Occurrence & epidemiology

Epidemiology

• The amniotic cavity is normally sterile; the frequency of microbial invasion depends on the setting: in preterm labour with intact membranes organisms are cultured from amniotic fluid in about 10%, in PPROM in about 32%.

Aetiopathogenesis

Aetiology and risk factors

• The infection usually ascends from the lower genital tract via the cervix, decidua and membranes into the amniotic cavity and is often polymicrobial; Listeria monocytogenes, by contrast, reaches it haematogenously.
• The most frequent organisms are ureaplasmas and mycoplasmas; genital tract organisms such as group B streptococci also play a role.

Clinical features

Clinical features and complications

• Fever is typical, together with maternal and fetal tachycardia, uterine tenderness, foul-smelling amniotic fluid and purulent cervical discharge; the infection may, however, be subclinical.
• For the fetus and neonate the risk of preterm birth, low Apgar scores, sepsis, pneumonia, meningitis, seizures, cerebral palsy and death increases; chronic chorioamnionitis is associated with chronic lung disease, retinopathy of prematurity and impaired brain development.
• Maternal risks include bacteraemia, uterine atony, postpartum haemorrhage, pelvic abscess, thromboembolism, wound complications and placental abruption, and less often septic shock and disseminated intravascular coagulation.

Histology

• Acute histological chorioamnionitis is characterised by neutrophils in the chorioamniotic membranes or chorionic plate and represents a maternal inflammatory response.

Diagnosis

Criteria

• Fever counts from 39.0 °C (1x) or ≥38.0 °C (2x, 30 min apart).
• Additional criteria are fetal tachycardia >160, maternal leukocytosis >15,000.

• For laboratory confirmation, amniotic fluid is obtained by amniocentesis and tested for inflammation, such as white cells, glucose and interleukin-6, and for organisms by Gram stain, culture or molecular tests.
• A single sign is unreliable, as fetal tachycardia, for example, may have other causes.

Keep learning in the app

Further reading (selection)

1. StatPearls: Chorioamnionitis (NCBI Bookshelf)
2. MSD Manual Professional Edition: Intraamniotic Infection
3. DocCheck Flexikon, Amnioninfektionssyndrom

Cross-references