Chorioamnionitis


Chorioamnionitis, also known as intra-amniotic infection, is an inflammation of the fetal membranes most commonly due to a bacterial infection. Recently, experts have suggested using the term intrauterine inflammation or infection or both, or Triple I, instead of the term chorioamnionitis, as a way to illustrate that a febrile mother is not an automatic confirmation of chorioamnionitis, or a reason to automatically begin antibiotics. Chorioamnionitis typically results from an infection caused by bacteria ascending from the vagina into the uterus but is also associated with premature or prolonged labor. The risk of developing chorioamnionitis increases with number of vaginal examinations performed in the final month of pregnancy, including during labor, as well as with tobacco and alcohol use.
Prevention of chorioamnionitis can occur by administering antibiotics if the amniotic sac bursts prematurely, or by collecting subjective and objective data from the patient, such as if the patient is febrile, has pain abdominally, or is experiencing abnormal excretion vaginally.

Anatomy

The amniotic sac consists of two parts:
The sign and symptoms of clinical chorioamnionitis can include:
For mother and fetus, chorioamnionitis may lead to further short and long-term issues.

Maternal complications

In the long-term, infants may be more likely to experience cerebral palsy or neurodevelopmental disabilities, which seems to be related to the activation of the fetal inflammatory response syndrome. This systemic response results in neutrophil and cytokine release that can impair the fetal brain and other vital organs. 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.

Causes

Causes of chorioamnionitis have been found to stem from microorganism infection as well as obstetric and other related factors.

Microorganisms

Bacterial, viral, and even fungal infections have been found to cause chorioamnionitis with the most common occurring from Ureaplasma, Fusobacterium, and Streptococcus bacteria species. Less commonly, Gardnerella, Mycoplasma, and Bacteroids bacterial species, as well as sexually transmitted infections of chlamydia and gonorrhea, have been implicated in the development of the condition as well. Studies are continuing to identify other microorganism classes and species as infection sources.

Obstetric and other

In addition to microorganism causes, birthing-related events, lifestyle, and ethnic background have been linked to an increase in the risk of developing chorioamnionitis. Premature deliveries, ruptures of the membranes of the amniotic sac, prolonged labors, and first time giving birth have been associated with this condition. At term women who experience a combination of pre-labor membrane ruptures and multiple invasive vaginal examinations, prolonged labors, or have meconium appear in the amniotic fluid are at higher risk than at term women experiencing just one of those events. In other studies, smoking, alcohol use and drug use have been noted as risk factors in addition to an increased risk for those of African American ethnicity.

Diagnosis

Pathologic

Chorioamnionitis can be diagnosed from a histologic examination of the fetal membranes. Of note, 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 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 and, if very severe, funisitis.

Suspected clinical diagnosis

When intrapartum fever is higher than 39.0°C, a 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:
Diagnosis is typically not confirmed until after delivery. However, patients 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 test results such as gram staining, glucose levels, or other culture results are consistent with infection.

Prevention

If the amniotic sac breaks early into pregnancy, the potential of introducing bacteria in the amniotic fluid can increase, yet administering antibiotics maternally can potentially prevent chorioamnionitis and allow for a longer pregnancy.  In addition, it has been shown that it is not necessary to deliver the fetus quickly after chorioamnionitis is diagnosed, so a C-section is not necessary unless it is necessary for maternal reasons. However, research has found that beginning labor early at approximately 34 weeks can lessen the likelihood of fetal death, and reduce the potential for excessive infection within the mother.
In addition, providers should interview patients of more subjective characteristics at scheduled obstetrics visits during pregnancy, including whether the patient has experienced excretion vaginally, whether the patient reports signs of being febrile, or if their abdominal area has been hurting.

Treatment

The American College of Obstetricians and Gynecologists' Committee Opinion proposes the use of antibiotic treatment in intrapartum patients with suspected or confirmed chorioamnionitis and intrapartum patients with maternal fever without an identifiable cause.
Antibiotic treatment consists of:
However, there is not enough evidence to support the most efficient antimicrobial regimen, starting the treatment during the intrapartum period is more effective than starting it postpartum; it shortens the hospital stay for the mother and the neonate. However, completion of treatment/cure is only considered after delivery.

Outcomes

Chorioamnionitis has been found to have possible associations with numerous neonatal conditions. Intrapartum chorioamnionitis may be associated with neonatal pneumonia, meningitis, sepsis, and death, as well as long-term infant complications like bronchopulmonary dysplasia and cerebral palsy. In addition to the possible associations, chorioamnionitis may act as a risk factor for premature birth and periventricular leukomalacia.

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, 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 patients of African American ethnicity, patients with immunosuppression, and patients who smoke, use alcohol, or abuse drugs.