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Intra-Amniotic Infection

(Chorioamnionitis)

By Antonette T. Dulay, MD, Attending Physician, Maternal-Fetal Medicine Section, Department of Obstetrics and Gynecology;Senior Physician, Main Line Health System;Axia Women’s Health

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Intra-amniotic 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.

Intra-amniotic infection typically results from an infection that ascends through the genital tract.

Risk factors

Risk factors for intra-amniotic infection include the following:

  • Nulliparity

  • Meconium-stained amniotic fluid

  • Internal fetal or uterine monitoring

  • Presence of genital tract pathogens (eg, group B streptococci)

  • Multiple digital examinations during labor in women with ruptured membranes

  • Prolonged rupture of membranes (a delay of ≥ 18 to 24 h between rupture and delivery)

Complications

Intra-amniotic infection can cause as well as result from preterm PROM or preterm delivery. This infection accounts for 50% of deliveries before 30 wk 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 complications include increased risk of the following:

  • Preterm delivery

  • Apgar score < 3

  • Neonatal infection (eg, sepsis, pneumonia, meningitis)

  • Seizures

  • Cerebral palsy

  • Death

Maternal complications include increased risk of the following:

  • Bacteremia

  • Need for cesarean delivery

  • Uterine atony

  • Postpartum hemorrhage

  • Pelvic abscess

  • Thromboembolism

  • Wound complications

  • Abruptio placentae

Septic shock, coagulopathy, and acute respiratory distress syndrome are also risks but are uncommon if infection is treated.

Symptoms and Signs

Intra-amniotic 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

  • Clinical criteria

  • 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.)

In the diagnosis of intra-amniotic infection, findings may be categorized as follows (1):

  • 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 min (isolated maternal fever does not automatically lead to a diagnosis of infection)

  • Suspected intra-amniotic infection based on maternal fever and clinical criteria (elevated maternal WBC count, fetal tachycardia, purulent cervical discharge)

  • Confirmed intra-amniotic infection: Suspected intra-amniotic infection that 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 intra-amniotic infection is absent, heart rate returns to baseline as these conditions resolve.

Intra-amniotic infection is usually confirmed after delivery.

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/μL

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

  • Broad-spectrum antibiotics, antipyretics, plus delivery

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

Treatment of intra-amniotic infection is recommended when

  • Intra-amniotic 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.

Intra-amniotic infection is treated with broad-spectrum IV antibiotics plus delivery.

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

  • Ampicillin 2 g IV q 6 h

  • Gentamicin 2 mg/kg IV (loading dose) followed by 1.5 mg/kg IV q 8 h, or gentamicin 5 mg/kg IV q 24 h

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 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.

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

Prevention

Risk of intra-amniotic infection is decreased by avoiding or minimizing digital pelvic examinations in women with preterm PROM.

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

  • Intra-amniotic infection can be subclinical and relatively asymptomatic.

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

  • Consider analyzing and culturing amniotic fluid if women have refractory preterm labor or preterm PROM.

  • Treat suspected or confirmed intra-amniotic 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).