Management of Pregnant Women With Presumptive Exposure to Listeria monocytogenes
ABSTRACT: Listeriosis is predominantly a foodborne illness, with sporadic and outbreak-related cases tied to
consumption of food contaminated with listeria (Listeria monocytogenes). The incidence of listeriosis associated
with pregnancy is approximately 13 times higher than in the general population. Maternal infection may present
as a nonspecific, flu-like illness with fever, myalgia, backache, and headache, often preceded by diarrhea or other
gastrointestinal symptoms. However, fetal and neonatal infections can be severe, leading to fetal loss, preterm
labor, neonatal sepsis, meningitis, and death. Pregnant women have been advised to avoid foods with a high risk
of contamination with listeria. An exposed pregnant woman with a fever higher than 38.1°C (100.6°F) and signs
and symptoms consistent with listeriosis for whom no other cause of illness is known should be simultaneously
tested and treated for presumptive listeriosis. No testing, including blood and stool cultures, or treatment is indicated
for an asymptomatic pregnant woman who reports consumption of a product that was recalled or implicated
during an outbreak of listeria contamination. A pregnant woman who ate a product that was recalled because of
listeria contamination and who is afebrile but has signs and symptoms consistent with a minor gastrointestinal or
flu-like illness can be managed expectantly.
Listeriosis is predominantly a foodborne illness, with sporadic
and outbreak-related cases tied to consumption of
food contaminated with listeria (Listeria monocytogenes)
(1–6). Listeria is an aerobic and facultative anaerobic,
gram-positive bacillus that is found readily in the environment.
Invasive listeriosis, defined as isolation of listeria
from a normally sterile site (typically blood or cerebrospinal
fluid), is uncommon. Although there are no prospective
data to guide recommendations for the care of
pregnant women with known or presumptive exposure
to listeria, outbreak-related cases of listeriosis have highlighted
the need for such guidance. This Committee
Opinion provides background information on listeriosis
in pregnancy as well as management recommendations,
largely based on expert opinion, for known or suspected
cases of listeriosis in pregnancy that are associated with
outbreaks and product recalls.
In 2010, there were a reported 0.27 cases of listeriosis
per 100,000 people in the United States (7). However,
the incidence of listeriosis associated with pregnancy
is approximately 13 times higher than in the general
population (8). The incidence of pregnancy-associated
listeriosis is markedly higher among Hispanic women
(8.9 per 100,000) compared with non-Hispanic women
(2.3 per 100,000) (8). Nearly all pregnancy-associated
cases of listeriosis occur in otherwise healthy women with
no additional predisposing risk factors (9). Although listeriosis
has been diagnosed mainly in the third trimester,
the incidence at earlier gestational ages may be underreported
because of the relative infrequency of culturing
products of conception in cases of early fetal loss (10).
Maternal and Perinatal Outcomes
Maternal infection may be asymptomatic. When it is
symptomatic, infection generally presents as a nonspecific,
flu-like illness with fever, myalgia, backache, and
headache, often preceded by diarrhea or other gastrointestinal
symptoms (9, 11). However, fetal and neonatal
infections can be severe, resulting in fetal loss, preterm
labor, neonatal sepsis, meningitis, and death. A case series
of 11 pregnant women with listeriosis and an accompanying
review of 222 cases in the literature found that
Committee on Obstetric Practice
This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The information should
not be construed as dictating an exclusive course of treatment or procedure to be followed.
The American College of
Obstetricians and Gynecologists
WOMEN’S HEALTH CARE PHYSICIANS
2 Committee Opinion
approximately one in five pregnancies complicated by
listeriosis resulted in spontaneous abortion or stillbirth;
approximately two thirds of surviving infants developed
clinical neonatal listeriosis (9). Active, population-based
surveillance for listeriosis determined that 17% of 760
listeriosis cases reported in 10 U.S. geographic sites from
2004 to 2009 were associated with pregnancy, with an
overall perinatal mortality (fetal loss or neonatal death)
rate of 29% (8).
In the United States, efforts have been aimed at the prevention
of listeriosis, including reducing listeria contamination
of ready-to-eat foods, such as processed meats;
proper food preparation and storage; and general food
safety, hygiene, and sanitation, with information on safe
practices found at www.cdc.gov/listeria/prevention (12).
In addition, women have been advised to avoid high-risk
foods during pregnancy (Box 1). Although recommendations
exist for treating pregnant women with listeriosis
(10, 13, 14), few guidelines exist for management of cases
of possible exposure in pregnancy. High-profile listeriosis
outbreaks, such as the multistate outbreak in the fall of
2011 and the resultant publicized recall of cantaloupes
grown on a single farm, highlight the need for such
The following recommendations provide guidance
for the management of pregnant women with presumptive
exposure to listeria in three clinical scenarios: women
who are 1) asymptomatic, 2) mildly symptomatic but
afebrile, and 3) febrile with or without other symptoms
of listeriosis (see Fig. 1).
No testing, including blood and stool cultures, or treatment
is indicated for an asymptomatic pregnant woman
who reports consumption of a product that was recalled
or implicated during an outbreak of listeria contamination.
An asymptomatic patient should be instructed to
return if she develops symptoms of listeriosis within
2 months of eating the recalled or implicated product.
There is no reason to alter or begin fetal surveillance in
asymptomatic women with known or presumptive exposure
Mildly Symptomatic but Afebrile
There are no data to guide the management of an exposed,
afebrile pregnant woman with mild symptoms that do not
strongly suggest listeriosis. A pregnant woman who ate a
product that was recalled because of listeria contamination
and who is afebrile but has signs and symptoms consistent
with a minor gastrointestinal or flu-like illness (such as
mild myalgia, mild nausea, vomiting, or diarrhea) can
be managed expectantly (ie, the same as for an exposed,
asymptomatic pregnant woman). This is a reasonable
approach that limits low-yield testing. Alternatively, such
a patient could be tested with blood culture for listeria,
but if such a course is elected, specific instruction should
be given to the microbiology laboratory. Because the
morphology of listeria resembles that of diphtheroids, it
may be mistaken for a contaminant (9). Therefore, the
laboratory should be alerted to the clinical suspicion of
listeriosis. If such diagnostic testing is performed, some
experts would withhold antibiotic therapy unless the
culture yielded listeria. Others would initiate antibiotic
therapy, although no effectiveness data exist to help clinicians
and patients evaluate the risks and benefits of such
a treatment choice. If testing is undertaken and the blood
culture yields listeria, standard antimicrobial treatment
for listeriosis, typically including intravenous ampicillin,
would be indicated (see following section). Assessments of
fetal well-being should be addressed on an individualized
basis with consideration given to the degree of concern for
infection and the patient’s clinical status.
Febrile With or Without Other Symptoms
Consistent With Listeriosis
An exposed pregnant woman with a fever higher than
38.1°C (100.6°F) and signs and symptoms consistent with
listeriosis for whom no other cause of illness is known
should be simultaneously tested and treated for presumptive
Diagnosis is made primarily by blood culture.
Placental cultures should be obtained in the event of
delivery. If blood cultures are negative after the recommended
antibiotic regimen has begun, the decision about
whether or not to continue antibiotics should be made
using clinical judgment combined with consultation(s)
with an infectious disease specialist, a maternal–fetal
medicine specialist, or both.
Box 1. Foods With a High Risk
of Contamination With Listeria
Pregnant women should avoid eating the following foods:
• Hot dogs, lunch meats, cold cuts (when served chilled
or at room temperature; heat to internal temperature of
74°C [165°F] or steaming hot)
• Refrigerated pâté and meat spreads
• Refrigerated smoked seafood
• Raw (unpasteurized) milk
• Unpasteurized soft cheeses such as feta, queso
blanco, queso fresco, Brie, queso panela, Camembert,
and blue-veined cheeses
• Unwashed raw produce such as fruits and vegetables
(when eating raw fruits and vegetables, skin should be
washed thoroughly in running tap water, even if it will
be peeled or cut)
Data from Centers for Disease Control and Prevention. Listeria
(listeriosis). Prevention. Available at: http://www.cdc.gov/listeria/
prevention.html. Retrieved July 25, 2014.
Committee Opinion 3
In the aforementioned clinical scenarios, management
guidance does not include stool culture for listeria
because such cultures have not been validated as a screening
tool and are not recommended for the diagnosis of
listeriosis. Ingestion of listeria occurs frequently because
the bacterium is commonly present in the environment.
Therefore, intermittent fecal carriage and shedding of
listeria are also frequent (approximately 5% in unselected
populations, but substantial variation exists) and rarely
indicative of infection (10). Furthermore, stool culture
for listeria may have low sensitivity and is not available in
most clinical laboratories.
Listeriosis is predominantly a foodborne illness caused by
consumption of food contaminated with the bacterium
listeria. Pregnant women are about 13 times more likely
than the general population to get listeriosis (8). Maternal
infection may manifest as a nonspecific, flu-like illness
with fever but can result in severe fetal and neonatal
infection, leading to fetal loss, preterm labor, neonatal
sepsis, meningitis, and death. Pregnant women should be
advised to avoid foods with a high risk of contamination
with listeria (see Box 1). Management recommendations
for cases of known or suspected listeria exposure during
pregnancy, such as those associated with an outbreak or
product recall, are summarized in Figure 1.
Listeria survives and grows within host cells, so
infection does not respond favorably to bacteriostatic
antibiotics. The antimicrobial regimen of choice for treatment
of listeriosis is high-dose intravenous ampicillin (at
least 6 g/day) for nonallergic patients for at least 14 days
(14). Frequently, gentamicin is added to the treatment
regimen because it has demonstrated synergism with
ampicillin (16), although not all authorities agree that
this adds to the effectiveness of the regimen, especially
given the toxicity of gentamicin (14). Women who are
allergic to penicillin, ampicillin, or both present a clinical
conundrum; trimethoprim with sulfamethoxazole is the
generally recommended alternative to ampicillin (14).
The Centers for Disease Control and Prevention considers
listeriosis a nationally notifiable disease, and once
diagnosis is confirmed, health care providers should contact
their state public health departments to comply with
local requirements for reporting.
Although blood cultures are the standard for diagnosis
in cases of fever and symptoms consistent with listeriosis,
if an amniocentesis has been performed, it usually
reveals meconium staining and gram-positive rods (17).
This information may help guide management when the
diagnosis is uncertain (18).
Initiating a program of fetal surveillance seems
prudent for women in whom listeriosis is diagnosed or
strongly suspected because of exposure and fever with or
without other symptoms, although studies and data do
not exist to point to one best plan for such testing.
Fig. 1. Management of pregnant women with presumptive exposure to listeria.
Abbreviation: IV, intravenous.
*Symptoms include flu-like symptoms, such as myalgia, abdominal or back pain, nausea, vomiting, or diarrhea.
†Trimethoprim with sulfamethoxazole should be used if patient is allergic to penicillin.
Presumptive exposure to listeria
Is patient symptomatic?*
Is patient febrile? No testing or treatment
• Expectant management
• May consider obtaining blood
• Simultaneous testing with blood
cultures and treatment with IV
• Obtain placental culture if
4 Committee Opinion
9. Mylonakis E, Paliou M, Hohmann EL, Calderwood SB,
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12. Centers for Disease Control and Prevention. Listeria (listeriosis):
prevention. Available at: http://www.cdc.gov/
listeria/prevention.html. Retrieved July 29, 2014.
13. Silver HM. Listeriosis during pregnancy. Obstet Gynecol
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15. Centers for Disease Control and Prevention. Multistate outbreak
of listeriosis linked to whole cantaloupes from Jensen
Farms, Colorado. Atlanta (GA): CDC; 2012. Available at:
082712/index.html. Retrieved July 29, 2014.
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