Intraamniotic infection is infection and resulting inflammation of the chorion, amnion, amniotic fluid, placenta, decidua, fetus, 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 and is often polymicrobial. Listeria monocytogenes, a cause of listeriosis, causes hematogenous intraamniotic infection.
Risk factors
Risk factors for intraamniotic infection include the following:
Prolonged rupture of membranes (a delay of ≥ 18 to 24 hours between rupture and delivery)
Meconium-stained amniotic fluid
Presence of genital tract pathogens (eg, group B streptococci)
Multiple digital examinations during labor in women with ruptured membranes
Internal fetal or uterine monitoring
Complications
Intraamniotic infection can cause as well as result from preterm PROM or preterm labor.
Fetal or neonatal complications include increased risk of the following:
Preterm delivery
Apgar score < 3
Neonatal infection (eg, sepsis, pneumonia, meningitis)
Seizures
Death
Maternal complications include increased risk of the following:
Bacteremia
Need for cesarean delivery
Uterine atony
Pelvic abscess
Wound complications
Septic shock, disseminated intravascular coagulation, and acute respiratory distress syndrome are also potential complications but are uncommon if infection is treated.
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 during labor without other identifiable cause
Amniocentesis for suspected subclinical infection
Intraamniotic infection is suspected and diagnosed based on clinical and sometimes laboratory criteria. There are 3 diagnostic categories (1):
Isolated maternal fever: A single oral temperature of ≥ 39° C or an oral temperature of 38 to 38.9° C that is still present when the temperature is measured again after 30 minutes (isolated maternal fever does not automatically lead to a diagnosis of infection)
Suspected intraamniotic infection: Maternal fever and one or more of the following: elevated maternal white blood cell [WBC] count, fetal tachycardia, or purulent cervical discharge
Confirmed intraamniotic infection: Sometimes further evaluation is indicated to confirm intraamniotic infection by amniotic fluid tests (Gram staining, culture, glucose level) or histologic evidence of placental infection or inflammation
Subclinical infection
Refractory preterm labor (persisting despite tocolysis) may suggest subclinical infection. If membranes rupture prematurely before term, clinicians should consider subclinical infection to 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 bacteria or leukocytes using Gram staining
Glucose level < 14 mg/dL
WBC count > 30 cells/mcL
Trace or greater leukocyte esterase activity (tested with urine dipstick reagent strip)
Positive culture
Other diagnostic tests for subclinical infection are under study.
Diagnosis reference
1. American College of Obstetricians and Gynecologists: Committee Opinion No. 712: Intrapartum Management of Intraamniotic Infection. Obstet Gynecol. 2017 (reaffirmed 2022); 130(2):e95-e101. doi:10.1097/AOG.0000000000002236
Treatment of Intraamniotic Infection
Broad-spectrum antibiotics covering gram positives, gram negatives, and anaerobes
Antipyretics
Delivery as indicated
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 and delivery (see table Recommended Antibiotic Regimens for Treatment of Intraamniotic Infection).
A typical intrapartum antibiotic regimen (for a patient with no allergy to penicillin) consists of both of the following:
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.
1).
Intraamniotic infection alone is rarely an indication for cesarean delivery. Informing the neonatal care team when intraamniotic infection is suspected or confirmed and which risk factors are present is essential to optimize evaluation and treatment of the neonate.
Treatment reference
1. Lieberman E, Lang J, Richardson DK, et al: Intrapartum maternal fever and neonatal outcome. Pediatrics 105(1 Pt 1):8-13, 2000. doi:10.1542/peds.105.1.8
Prevention of Intraamniotic Infection
Risk of intraamniotic 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.
Universal screening for group B streptococcus should be performed at 35 to 37 weeks gestation for all pregnant patients, and patients who screen positive should be given antibiotic prophylaxis during labor.
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.
