Article Author:
Josephine Fowler
Article Editor:
Leslie Simon
1/9/2019 11:06:38 AM
PubMed Link:


Chorioamnionitis is an infection that can occur before labor, during labor, or after delivery. It can be acute, subacute, or chronic. Subacute chorioamnionitis is associated with chronic lung disease in the infant.[1] Chronic chorioamnionitis is associated with retinopathy of prematurity, very low birth weight, and impaired brain development in the premature infant. Chronic chorioamnionitis is common.[2][3][4] This terminology refers to histologic chorioamnionitis. Histologic chorioamnionitis at term is rarely infectious.

In general, the clinical presentation of chorioamnionitis is defined as acute chorioamnionitis. The Greek etymology of the words chorion and amnion mean fetal membrane and itis means inflammation. Further description denotes chorioamnionitis includes the amniotic fluid. Chorioamnionitis may be identified postdelivery or postmortem on a pathologic review of the placenta and cord. In histologic chorioamnionitis, symptoms may be absent, and the placenta or cultures may not show evidence of chorioamnionitis.

Most commonly, chorioamnionitis is associated with preterm labor, prolonged rupture of membranes, prolonged labor, tobacco use, nulliparous pregnancy, meconium stained fluid, multiple vaginal exams post rupture of membranes, and in women with known bacterial or viral infections. However, it can occur at term and in women without prior infections. Left untreated, chorioamnionitis can lead to morbidity and mortality for the mother and neonate. Neonatal morbidity and mortality increase in severity and occurrence with earlier gestations. Antibiotic therapy has been shown to reduce the incidence and severity of the infection in both the mother and neonate. However, antibiotics do not eradicate the infection in all cases.


The literature defines chorioamnionitis as an inflammatory and infectious process. Inflammation in utero is linked to preterm birth, brain abnormalities, and retinopathy.[5][6][7] Infection can be due to a bacterial, fungal, or viral agent. Bacterial agents in chorioamnionitis can vary depending on the geographic location and population. Common bacterial agents found in chorioamnionitis include group B streptococcus, Mycoplasma pneumoniae[8], Ureaplasma, Gardnerella vaginalis, Escherichia coli, and Bacteroides. Candida species are identified as risk factors for chorioamnionitis, leading to preterm birth and adverse fetal outcomes.[9][10] In adolescents with sexually transmitted infections, studies show that trichomoniasis is a risk factor for the development of chorioamnionitis. Although chorioamnionitis is a risk factor for vertical transmission in pregnancy, the incidence of chorioamnionitis in HIV-positive versus HIV-negative women is not significantly different during labor. In one study of 298 women with similar risk factors and demographics, both groups of women had a high incidence of chorioamnionitis. The higher incidence for each group was strongly associated with the number of vaginal exams during labor.[11]


Chorioamnionitis occurs in about 4% of deliveries at term but occurs more frequently in preterm deliveries and premature rupture of membranes. In evaluating women with symptoms of chorioamnionitis, studies show a strong correlation between histologic chorioamnionitis and the key clinical symptoms of fever, uterine tenderness, meconium aspiration syndrome, and foul-smelling vaginal discharge.[12][13] Histologic chorioamnionitis with vasculitis is associated with a higher incidence of premature rupture of membranes and preterm delivery.[5]

In deliveries between 21 and 24 weeks gestation, chorioamnionitis can be found in more than 94% of the placentas on evaluation.[14] Term deliveries of mothers with chorioamnionitis are associated with failure to progress. Chorioamnionitis in preterm labor is likely to end in preterm delivery. Studies show that inflammation of the placenta or chorioamnionitis can be found in approximately 8% to 50% of preterm deliveries.[15][16] In the term pregnancy, chorioamnionitis is most likely associated with labor and a history of prolonged ruptured membranes.


Chorioamnionitis is an ascending infection, originating in the lower genitourinary tract and migrating to the amniotic cavity. The infection usually originates from the cervical and vaginal area. Vertical transmission has been documented in bacterial and viral infections transmitted to the fetus.[8]


Chorioamnionitis is an inflammatory process that ranges from mild to severe. Histopathologic findings consistent with inflammation also can be present in placentas of women with normal pregnancy.[17]

In chorioamnionitis, the membranes may appear normal or show evidence of infection. Fluid can be clear or cloudy. On histologic examination, there is neutrophilic infiltration into the decidua, and in more severe cases, microabscesses are present on the decidua. A recent study suggests that neutrophils in the amniotic cavity are mostly of fetal origin. In extreme prematurity, both maternal and fetal neutrophils are more likely to be present in the amniotic cavity with chorioamnionitis.[18]

History and Physical

The initial history should include maternal age, gestational age, parity, highlights of the pregnancy including any complications, whether membranes are ruptured or intact, the presence of meconium, presence of or history of sexually transmitted infections, urinary tract infections, and recent illness. The physical exam must be thorough and include vitals and a complete physical evaluation including the abdomen, vagina, and uterus.

Chorioamnionitis presents as a febrile illness associated with an elevated white blood cell (WBC) count, uterine tenderness, abdominal pain, foul-smelling vaginal discharge, and fetal and maternal tachycardia. Diagnosing clinical chorioamnionitis includes a fever of at least 38 C (100.4 F) and one of the clinical symptoms or between 38 C (100.4 F) and 39 C (102.2 F) within 30 minutes. The majority of women presenting with chorioamnionitis are in labor or have ruptured membranes when it presents.


Initial evaluation for chorioamnionitis includes a thorough clinical assessment of the mother and fetus. Although the maternal WBC count is a routine test done when there is suspicion of an infection, recent studies show that the WBC count does not identify the presence of microbial invasion or inflammation in the amniotic cavity for women with premature rupture of membranes on admission.[19]The WBC count also has low sensitivity and specificity. Bacterial cultures taken from the cervix are not indicated and do not correlate with infection secondary to chorioamnionitis.[20]

Treatment / Management

The primary management of chorioamnionitis is antibiotic therapy. The most common antibiotics used are ampicillin and gentamicin. Alternative antibiotics include clindamycin, cefazolin, and vancomycin in women allergic to penicillin. After delivery, the current recommendation is to administer one additional dose with a cesarean section but no additional antibiotics for vaginal deliveries. Additional broad-spectrum antibiotics may be required, depending on the clinical status.[21]

Differential Diagnosis

Abdominal pain and uterine tenderness associated with fever are nonspecific signs. Women with fever, pain, and tenderness during labor must be evaluated for other common infections such as appendicitis, urinary tract infection, pyelonephritis, and pneumonia. Additional ancillary testing and examination must be thoroughly reviewed before making a final diagnosis.


Chorioamnionitis is a risk factor for both maternal and neonatal sequelae. Endometritis can occur in up to one-third of women treated for chorioamnionitis who undergo a cesarean section. The rate of endometritis is the same in vaginal deliveries and cesarean deliveries following chorioamnionitis. Recent studies show that management with postpartum antibiotics does not decrease the risk of endometritis following chorioamnionitis.[22]

The majority of women with chorioamnionitis will recover and not require further antibiotics after delivery.


Neonatal complications of chorioamnionitis include premature birth, cerebral palsy, retinopathy of prematurity, neurologic abnormalities, respiratory distress syndrome, bronchopulmonary dysplasia in premature infants, neonatal sepsis, and neonatal death. Neonatal sepsis is suspected as a complication of chorioamnionitis; however, in more than 99% of cases, cultures are negative. Perinatal listeriosis is associated with high morbidity. Current antibiotic regimens may not cover listeriosis in chorioamnionitis.

Maternal complications of chorioamnionitis include severe pelvic infections, subcutaneous wound infections, preterm delivery, postpartum hemorrhage, operative delivery, and maternal sepsis.

Chorioamnionitis is associated with vertical transmission of HIV in pregnancy.[23][24]

Deterrence and Patient Education

Patients who are pregnant should receive routine counseling at each prenatal visit. Education should include reporting rupture of membranes, vaginal discharge, fever, and abdominal pain to their obstetrical provider. Every woman should receive information on risk factors and signs and symptoms of infection during the prenatal period.

Enhancing Healthcare Team Outcomes

Women presenting with abdominal pain, uterine tenderness, and fever during labor must be evaluated for other causes. In women with premature rupture of membranes, the team must consider the risk of multiple examinations and avoid multiple digital exams. Nursing and physician communication is important to assure the initial examination is done with a sterile speculum. Clear communication also is required between team members to make sure the physician is alerted to any changes in pain, fever, or clinical status.

When choosing antibiotics, medical records should be reviewed thoroughly giving special attention to the history of allergies and any previous reactions to penicillin or any other antibiotics. This information must be reported to the pharmacy when ordering medication and reviewed by the team.

If the patient requires a cesarean section, these items must be reviewed again during the time out in the operating room.