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Intraamniotic Infection

(Chorioamnionitis)

By

Antonette T. Dulay

, MD, Main Line Health System

Last review/revision Oct 2022
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Intraamniotic infection is infection of the chorion, amnion, amniotic fluid, placenta, or a combination. Infection increases risk of obstetric complications and problems in the fetus and neonate. Symptoms include fever, uterine tenderness, foul-smelling amniotic fluid, purulent cervical discharge, and maternal or fetal tachycardia. Diagnosis is by specific clinical criteria or, for subclinical infection, analysis of amniotic fluid. Treatment includes broad-spectrum antibiotics, antipyretics, and delivery.

Intraamniotic infection typically results from an infection that ascends through the genital tract.

Risk factors

Risk factors for intraamniotic infection include the following:

Complications

Intraamniotic infection can cause as well as result from preterm PROM or preterm delivery. This infection accounts for 50% of deliveries before 30 weeks gestation. It occurs in 33% of women who have preterm labor with intact membranes, 40% who have PROM and are having contractions when admitted, and 75% who go into labor after admission for PROM.

Fetal or neonatal complications include increased risk of the following:

Maternal complications include increased risk of the following:

Symptoms and Signs of Intraamniotic Infection

Intraamniotic infection typically causes fever. Other findings include maternal tachycardia, fetal tachycardia, uterine tenderness, foul-smelling amniotic fluid, and/or purulent cervical discharge. However, infection may not cause typical symptoms (ie, subclinical infection).

Diagnosis of Intraamniotic Infection

  • Maternal fever without other identifiable cause

  • Amniocentesis for suspected subclinical infection

(See also American College of Obstetricians and Gynecologists’ Committee on Obstetric Practice: Committee Opinion No. 712: Intrapartum management of intraamniotic infection.)

  • Isolated maternal fever: A single oral temperature of ≥ 39° C or an oral temperature of ≥ 38 to 39° C that is still present when the temperature is measured after 30 minutes (isolated maternal fever does not automatically lead to a diagnosis of infection)

  • Suspected intraamniotic infection based on maternal fever and clinical criteria (elevated maternal white blood cell [WBC] count, fetal tachycardia, or purulent cervical discharge)

  • Confirmed intraamniotic infection: Sometimes suspected intraamniotic infection is confirmed by results of amniotic fluid tests (Gram staining, culture, glucose level—see below) or histologic evidence of placental infection or inflammation

Presence of a single symptom or sign, which may have other causes, is less reliable. For example, fetal tachycardia may be due to maternal use of drugs or fetal arrhythmia. However, if intraamniotic infection is absent, heart rate returns to baseline as these conditions resolve.

Intraamniotic infection is usually confirmed after delivery through correlation with placental pathology.

Subclinical infection

Refractory preterm labor (persisting despite tocolysis) may suggest subclinical infection. If membranes rupture prematurely before term, clinicians should also consider subclinical infection so that they can determine whether induction of labor is indicated.

Amniocentesis with culture of amniotic fluid can help diagnose subclinical infection. The following fluid findings suggest infection:

  • Presence of any bacteria or leukocytes using Gram staining

  • Positive culture

  • Glucose level < 15 mg/dL

  • WBC count > 30 cells/mcL

Other diagnostic tests for subclinical infection are under study.

Diagnosis reference

  • 1. Higgins RD, Saade G, Polin RA, et al: Evaluation and management of women and newborns with a maternal diagnosis of chorioamnionitis: Summary of a workshop. Obstet Gynecol 127 (3):426–436, 2016. doi: 10.1097/AOG.0000000000001246

Treatment of Intraamniotic Infection

  • Broad-spectrum antibiotics

  • Antipyretics

  • Delivery

(See also American College of Obstetricians and Gynecologists’ Committee on Obstetric Practice: Committee Opinion No. 712: Intrapartum management of intraamniotic infection.)

Treatment of intraamniotic infection is recommended when

  • Intraamniotic infection is suspected or confirmed.

  • Women in labor have an isolated temperature of ≥ 39° C and no other clinical risk factors for fever.

If women have a temperature of 38 to 39° C and no risk factors for fever, treatment can be considered.

Appropriate antibiotic treatment reduces morbidity in the mother and neonate.

As soon as intraamniotic infection is diagnosed, it is treated with broad-spectrum IV antibiotics plus delivery.

A typical intrapartum antibiotic regimen consists of both of the following:

  • Ampicillin 2 g IV every 6 hours

  • Gentamicin 2 mg/kg IV (loading dose) followed by 1.5 mg/kg IV every 8 hours or gentamicin 5 mg/kg IV every 24 hours

In addition, if delivery is cesarean, one additional dose of the chosen regimen plus a dose of clindamycin 900 mg IV or metronidazole 500 mg IV can be given after the umbilical cord is clamped.

Women with a mild penicillin allergy can be given

  • Cefazolin plus gentamicin

Women with a severe penicillin allergy can be given one of the following:

  • Clindamycin (or metronidazole) plus gentamicin

  • Vancomycin plus gentamicin

Vancomycin should be used in women who are colonized with group B streptococci (GBS) if

  • GBS is resistant to clindamycin or erythromycin unless clindamycin-inducible resistance testing is negative.

  • Antibiotic sensitivities are not available.

How long antibiotics are given varies, depending on individual circumstances (eg, how high the fever was, when the fever last spiked in relation to delivery).

Antibiotics should not automatically be continued after delivery; use should be based on clinical findings (eg, bacteremia, prolonged fever) and on risk factors for postpartum endometritis, regardless of the delivery route. Women who have a vaginal delivery are less likely to develop endometritis and may not require postpartum antibiotics. After cesarean delivery, at least one additional dose of antibiotics is recommended.

Antipyretics, preferably acetaminophen before delivery, should be given in addition to antibiotics.

Intraamniotic infection alone is rarely an indication for cesarean delivery. Informing the neonatal care team when intraamniotic infection is suspected or confirmed and what risk factors are present is essential to optimize evaluation and treatment of the neonate.

Prevention of Intraamniotic Infection

Broad-spectrum antibiotics are given to women with preterm PROM to prolong latency until delivery and decrease risk of infant morbidity and mortality.

Key Points

  • Intraamniotic infection is infection of the chorion, amnion, amniotic fluid, placenta, or a combination that increases risk of obstetric complications and problems in the fetus and neonate.

  • Consider the diagnosis when women have the classic symptoms of infection (eg, fever, purulent cervical discharge, uterine pain or tenderness) or when fetal or maternal tachycardia or refractory preterm labor is present.

  • Determine the white blood cell count, and consider analyzing and culturing amniotic fluid if women have refractory preterm labor or preterm PROM.

  • Treat suspected or confirmed intraamniotic infection with broad-spectrum antibiotics, antipyretics, and delivery.

  • Also treat women in labor if they have an isolated temperature of ≥ 39° C and no other clinical risk factors for fever.

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