Intra-amniotic Infection

Epidemiology & Risk Factors

• Pathophysiology: Ascending infection of polymicrobial vaginal/cervical flora (Ureaplasma, Mycoplasma, E. coli, GBS, anaerobes) into amniotic cavity.
• Risk factors:
  • Prolonged rupture of membranes (PROM) (>18 hrs).
  • Prolonged labor.
  • Multiple digital cervical exams.
  • Internal fetal/uterine monitoring (e.g., fetal scalp electrode, IUPC).
  • Pre-existing STI or lower genital tract infection (e.g., BV, GBS).
  • Nulliparity.

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Clinical Features

• Maternal fever (≥38.0°C / 100.4°F) is mandatory clinical criterion. c
• Associated features (≥1 required for clinical dx):
  • Fetal tachycardia (>160/min for >10 min).
  • Maternal tachycardia (>100/min).
  • Purulent/foul-smelling cervical discharge or amniotic fluid.
  • Maternal leukocytosis (WBC >15,000/mm³).
  • Uterine fundal tenderness.

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Diagnosis

• Initial/Screening: Clinical diagnosis based on maternal fever + ≥1 associated clinical feature.
• Key Labs:
  • CBC: Leukocytosis w/ left shift.
  • Blood cultures: Indicated if patient appears septic.
• Imaging/Monitoring:
  • Fetal Heart Rate (FHR) Monitoring: Fetal tachycardia, loss of variability, late decelerations (if uteroplacental insufficiency develops).
  • US: Evaluates fetal well-being, fluid volume, biophysical profile (BPP).
• Confirmatory/Gold Standard: Amniocentesis (rarely indicated; reserved for diagnostic uncertainty in PPROM):
  • Low glucose (<20 mg/dL).
  • High WBC count / (+) Gram stain & amniotic fluid culture.
  • High IL-6 level.

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Differential Diagnostics

• Epidural Fever: Diff by isolated maternal fever post-epidural analgesia without maternal/fetal tachycardia, uterine tenderness, purulent discharge, or fetal distress.
• Acute Appendicitis: Diff by localized RLQ tenderness (displaced superiorly in late pregnancy), (-) purulent cervical discharge, normal amniotic fluid, absence of uterine tenderness.
• Placental Abruption: Diff by painful vaginal bleeding, uterine hypertonicity/tetany, fetal distress; lacking maternal fever or purulent cervical discharge.
• Acute Pyelonephritis: Diff by CVA tenderness, dysuria, costovertebral angle pain; amniotic fluid & fetal heart tracing typically clear unless secondary sepsis occurs.

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Management

1. Stabilize & Antipyretics:
   • IV fluid resuscitation.
   • Acetaminophen (reduces maternal fever & secondary fetal tachycardia).
2. Immediate Broad-Spectrum IV Antibiotics:
   • Ampicillin + Gentamicin (first-line for planned vaginal delivery).
   • Add Clindamycin or Metronidazole if proceeding to C-section (covers anaerobes).
3. Immediate Delivery (Induction/Augmentation): c
   • Induce labor regardless of gestational age (infection is an absolute indication for delivery).
   • Intra-amniotic infection is NOT an indication for immediate C-section; C-section reserved strictly for standard OB indications (e.g., non-reassuring FHR tracing, malpresentation, failure to progress).
4. Postpartum Management:
   • Continue IV Abx until patient is afebrile & asymptomatic for ≥24 hrs.

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Complications

• Maternal:
  • Uterine atony & Postpartum Hemorrhage (PPH) (due to inflamed/dysfunctional myometrium).
  • Endometritis & pelvic abscess.
  • Septic pelvic thrombophlebitis (SPT).
  • Maternal sepsis & MODS.
• Fetal / Neonatal:
  • Neonatal sepsis & pneumonia.
  • Intraventricular hemorrhage (IVH).
  • Periventricular leukomalacia (PVL) & Cerebral palsy.
  • Bronchopulmonary dysplasia (BPD).
  • Neonatal death.