Abstract

Chorioamnionitis also known as intra-amniotic infection (IAI) is an inflammation of the fetal membranes (amnion and chorion) due to a bacterial infection. It typically results from bacteria ascending into the uterus from the vagina and is most often associated with prolonged labor. The risk of developing chorioamnionitis increases with each vaginal examination that is performed in the final month of pregnancy, including during labor.

Anatomy

The amniotic sac consists of two parts:

- The outer membrane is the chorion. It is closest to the mother and physically supports the much thinner amnion.

- The inner membrane is the amnion. It is in direct contact with the amniotic fluid, which surrounds the fetus.

Diagnosis | Clinical

Chorioamnionitis is diagnosed clinically in the setting of Maternal fever (≥ 100.4 °F) and at least two of the following:

- Maternal leukocytosis (> 15,000 cells/mm³)

- Maternal tachycardia (> 100 bpm)

- Fetal tachycardia (> 160 bpm)

- Uterine tenderness

- Foul odor of amniotic fluid

Exclusions:

- Maternal upper respiratory infection.

- Maternal urinary tract infection.

Diagnosis | Pathologic

Chorioamnionitis can be diagnosed from a histologic examination of the fetal membranes.

Infiltration of the chorionic plate by neutrophils is diagnostic of (mild) chorioamnionitis. More severe chorioamnionitis involves subamniotic tissue and may have fetal membrane necrosis and/or abscess formation.

Severe chorioamnionitis may be accompanied by vasculitis of the umbilical blood vessels (due to the fetus' inflammatory cells) and, if very severe, funisitis (inflammation of the umbilical cord's connective tissue).

Treatment

Antibiotic Treatment consists of:

- Standard: Ampicillin 2g IV every 6 hours + Gentamicin 1.5 mg/kg every 8 hours

- Alternative: Ampicillin-Sulbactam 3g IV every 5 hours, Ticarcillin-Clavulanate 3.1g IV every 4 hours, Cefoxitine 2g IV every 6 hours

- Cesarean Delivery: Ampicillin 2g IV every 6 hours + Gentamicin 1.5 mg/kg every 8 hours + Clindamycin 900 mg every 8 hours or Metronidazole 500 mg IV every 6 hours

- Penicillin-Allergy: Vancomycin 1g IV every 12 hours + Gentamicin 1.5 mg/kg every 8 hours

Completion of treatment/cure is only considered after delivery.

Associations

Chorioamnionitis is a risk factor for periventricular leukomalacia and cerebral palsy.