Chorioamnionitis

Background

• Ascending bacterial infection leading to inflammation of the amniotic cavity and chorioamnionic memranes
• Also called intraamniotic infection, amnionitis, amnionic fluid infection

Microbiology

• Usually polymicrobial
• Non-stainable:
  • Ureaplasma urealyticum (47%)
  • Mycoplasma hominis (30%)
• Gram-positives:
  • Group B streptococcus (15%)
  • Enterococcus faecalis
  • Staphylococcus aureus
  • Other streptococci
• Gram-negatives:
  • Escherichia coli (8%)
  • Other gram-negative bacilli
• Anaerobes:
  • Bacteroides (30%)
  • Gardnerella vaginalis (25%)
  • Fusobacterium
  • Peptostreptococcus, Peptococcus, Clostridium

Epidemiology

• 1 to 4% of all birth
• More common with preterm delivery, PROM, prolonged labour, smoking/alcohol/drug use, multiple vaginal examination, internal monitoring of labour, bacterial vaginosis, colonization by group B streptococcus, and nulliparity

Risk Factors

• Prolonged rupture of membranes (including PPROM) ≥12 hours or ≥18 hours
• Prolonged labour, with second stage >2 hours or active labour >12 hours
• Multiple digital exams with membrane rupture ≥3 exams
• Nulliparity
• Colonization with group B Streptococcus
• Bacterial vaginosis
• Alcohol and tobacco use
• Meconium-stained amniotic fluid
• Internal monitoring of the fetus
• Epidural anaesthesia

Clinical Manifestations

• Fever, tenderness over the uterine fundus, maternal tachycardia, fetal tachycardia
• May have purulent or malodorous amniotic fluid
• Can be complicated by endometritis, pelvic abscess, surgical site infection, bacteremia, postpartum hemorrhage, and poor neonatal outcomes

Management

• Typically treated with ampicillin q6h and gentamicin q8-24h until delivery, with or without clindamycin or metronidazole1
• Duration is until delivery followed by one further dose of antibiotics

Prevention

• In patients with preterm premature rupture of membranes (PPROM), the risk of chorioamnionitis is high and they should receive prophylactic ampicillin and erythromycin (or azithromycin) (per ORACLE I and II trials)1
  • Often given IV for 2 days followed by oral for a total of 7 to 10 days