Chorioamnionitis is an intra-amniotic infection that occurs during pregnancy. It complicates 1%-4% of pregnancies in the United States. The infection can include the placenta, fetus, and amniotic fluid, as well as the fetal membranes.

The pathogenesis of this condition is related to ascending bacteria from the lower genital tract invading the sterile amniotic cavity. These infections are often polymicrobial in origin. Risk factors include prolonged rupture of membranes, an increasing number of digital exams in a ruptured patient, prolonged labor, nulliparity, group B Streptococcus colonization, internal monitoring of the fetus, prior pregnancy with infection, and meconium-stained amniotic fluid.

To make the diagnosis, the American College of Obstetricians and Gynecologists (ACOG) guidelines specify the patient must have either a fever of 39.0°C (102.2°F) alone or a maternal temperature of 38.0°C-39.0°C (100.4°F-102.2°F), and at least one additional risk factor. Other risk factors identified by ACOG include fetal tachycardia, maternal leukocytosis, and/or foul-smelling discharge.

Other symptoms that may occur include fundal tenderness on exam and maternal tachycardia.

Infection can contribute to neonatal pneumonia, meningitis, sepsis, and death. It can also affect the mother, leading to dysfunctional labor, sepsis, postpartum uterine atony, acute respiratory distress syndrome, and even death.