Chorioamnionitis

Introduction

• Description: Chorioamnionitis is the inflammation of the fetal membranes. This may be associated with prolonged or premature rupture of the membranes or a primary cause of premature labor. A Eunice Kennedy Shriver National Institute of Child Health and Human Development expert panel proposed a descriptive term: “intrauterine inflammation or infection or both” abbreviated as “Triple I” to replace the term chorioamnionitis. The same panel recommended separating intraamniotic infection into three different categories: (1) isolated maternal fever, (2) suspected intraamniotic infection, and (3) confirmed intraamniotic infection. These distinctions are more important in the research setting and not for the acute care of the patient.

• Prevalence: More than 40% of premature deliveries. Most cases will be found in term pregnancies (2%–5% of term pregnancies).

• Predominant Age: Reproductive age.

• Genetics: No genetic pattern.

Etiology and Pathogenesis

• Causes: Infection by organisms that ascend from the vaginal canal, most often when the membranes have been ruptured. Studies indicate that bacteria (specifically Escherichia coli ) can permeate intact chorioamnionic membranes. Infection may also occur by hematogenous (eg, Listeria monocytogenes ), transabdominal, or transfallopian routes or after invasive procedures (eg, amniocentesis or chorionic villus sampling).

• Risk Factors: Prolonged rupture of the membranes, prolonged labor, internal uterine and fetal monitoring, multiple pelvic examinations (may not be independent of length of labor), low parity, bacterial or trichomonas vaginitis, vaginal or cervical infection with Chlamydia trachomatis, smoking, anemia, vaginal bleeding.

Signs and Symptoms

• May be asymptomatic

• Fever (>100.5°F, 38°C, 100% of cases); fever alone is insufficient to establish the diagnosis or to initiate antibiotic treatments

• Leukocytosis (70%–90%)

• Tachycardia (maternal and fetal, 40%–80%)

• Uterine irritability and tenderness (25%)

• May result in premature rupture of the membranes or preterm labor

• Maternal signs of infection (elevated white blood count and sedimentation rate)

• Purulent/malodorous cervical discharge (late)

Diagnostic Approach