Chorioamnionitis

Bacterial, viral, and even fungal infections can cause chorioamnionitis. Most commonly from Ureaplasma, Fusobacterium, and Streptococcus bacteria species. Less commonly, Gardnerella, Mycoplasma, and Bacteroides bacteria species. Sexually transmitted infections, chlamydia and gonorrhea, can cause development of the condition as well.[7] Studies are continuing to identify other microorganism classes and species as infection sources.[11]

Birthing-related events, lifestyle, and ethnic background have been linked to an increase in the risk of developing chorioamnionitis apart from bacterial causation.[11] Premature deliveries, ruptures of the amniotic sac membranes, prolonged labor, and primigravida childbirth are associated with this condition.[12] At term mothers who experience a combination of pre-labor membrane ruptures and multiple invasive vaginal examinations, prolonged labor, or have meconium appear in the amniotic fluid are at higher risk than at term mothers experiencing just one of those events.[11] In other studies, smoking, alcohol use and drug use are noted as risk factors. Those of African American ethnicity are noted to be at higher risk.[7][12]

Chorioamnionitis is diagnosed from a histologic (tissue) examination of the fetal membranes.[12] Confirmed histologic chorioamnionitis without any clinical symptoms is termed subclinical chorioamnionitis and is more common than symptomatic clinical chorioamnionitis.[2]

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.[1]

Severe chorioamnionitis may be accompanied by vasculitis of the umbilical blood vessels due to the fetus' inflammatory cells. If very severe, funisitis, inflammation of the umbilical cord connective tissue, occurs.[12]

The presence of fever between 38.0°C and 39.0°C alone is insufficient to indicate chorioamnionitis and is termed isolated maternal fever. Isolated maternal fever may not have an infectious cause and does not required antibiotic treatment.[2]

When intrapartum (during delivery) fever is higher than 39.0°C, suspected diagnosis of chorioamnionitis can be made. Alternatively, if intrapartum fever is between 38.0°C and 39.0°C, an additional risk factor must be present to make a presumptive diagnosis of chorioamnionitis. Additional risk factors include:[14]

• Fetal tachycardia
• Maternal leukocytosis (>15,000 cells/mm³)[15]
• Purulent cervical drainage

Diagnosis is typically not confirmed until after delivery. However, people with confirmed diagnosis and suspected diagnosis have the same post-delivery treatment regardless of diagnostic status. Diagnosis can be confirmed histologically or through amniotic fluid tests such as gram staining, glucose levels, or other culture results consistent with infection.[14]

Acetaminophen is often used for treating fevers and may be beneficial for fetal tachycardia. There can be increased likelihood for neonatal encephalopathy when mothers have intrapartum fever.[12]

For mother and fetus, chorioamnionitis may lead to short-term and long-term issues when microbes move to different areas or trigger inflammatory responses due to infection.[12]

• Higher risk for C-section
• Postpartum hemorrhage
• Endometritis[20]
• Bacteremia (often due to Group B streptococcus and Escherichia coli)[12]
• Pelvic abscess

Mothers with chorioamnionitis who undergo a C-section may be more likely to develop pelvic abscesses, septic pelvic thrombophlebitis, and infections at the surgical site.[11]

• Fetal death
• Neonatal sepsis

• Perinatal death
• Asphyxia
• Early onset neonatal sepsis[21]
• Septic shock
• Neonatal pneumonia
• Infant respiratory distress

In the long-term, infants may be more likely to experience cerebral palsy or neurodevelopmental disabilities. Disability development is related to the activation of the fetal inflammatory response syndrome (FIRS) when the fetus is exposed to infected amniotic fluid or other foreign entities.[4][12] This systemic response results in neutrophil and cytokine release that can impair the fetal brain and other vital organs.[4][9] Compared to infants with clinical chorioamnionitis, it appears cerebral palsy may occur at a higher rate for those with histologic chorioamnionitis. However, more research needs to be done to examine this association.[22] There is also concern about the impact of FIRS on infant immunity as this is a critical time for growth and development. For instance, it may be linked to chronic inflammatory disorders, such as asthma.[23]