The swelling of the amnion and chorion is characteristic of chorioamnionitis, occurring when bacteria makes its way into the amniotic fluid and creates an infection within the amniotic fluid. Diagnosis
Pathologic
Chorioamnionitis is diagnosed from a histologic (tissue) examination of the fetal membranes. Confirmed histologic chorioamnionitis without any clinical symptoms is termed subclinical chorioamnionitis and is more common than symptomatic clinical chorioamnionitis.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. If very severe, funisitis, inflammation of the umbilical cord connective tissue, occurs. Suspected clinical diagnosis
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.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:
Fetal tachycardia
Maternal leukocytosis (>15,000 cells/mm³)
Purulent cervical drainage

Confirmed diagnosis
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.
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. 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. Epidemiology
Chorioamnionitis is approximated to occur in about 4% of births in the United States. However, many other factors can increase the risk of chorioamnionitis. For example, in births with premature rupture of membranes (PROM), between 40 and 70% involve chorioamnionitis. Furthermore, clinical chorioamnionitis is implicated in 12% of all cesarean deliveries. Some studies have shown that the risk of chorioamnionitis is higher in those of African American ethnicity, those with immunosuppression, and those who smoke, use alcohol, or abuse drugs. See also
Chronic deciduitis
Funisitis
Placentitis
Whartons jelly

Notes
References
External links

Overview at Cleveland Clinic. Cerebral palsy inflammation link (29 November 2003) at BBC.