This sheet is about having Listeria infection (listeriosis) in a pregnancy or while breastfeeding. This information is based published research studies. It should not take the place of medical care and advice from your healthcare providers.
What is listeriosis?
Listeriosis is an infection caused by the bacteria Listeria monocytogenes, often called Listeria. Listeriosis is typically caused by eating food that has been contaminated with this bacterium. Listeria can be found everywhere, including your home, restaurants, and other places such as grocery stores and food processing plants. Food with Listeria can introduce the infection into the refrigerator where it can spread to other foods. Listeria can continue to live in cold temperatures, such as in the refrigerator, but the chance for spreading can be slowed if the refrigerator is kept at a temperature of 40°F / 4°C or lower.
Some foods that are more likely to be contaminated with Listeria include unpasteurized (raw) milk, and raw milk products, uncooked meat and fish, uncooked vegetables, deli meat, and soft cheeses. Listeria outbreaks can also be found on fruits, like cantaloupes and peaches.
What are the symptoms of listeriosis?
Not everyone infected with Listeria will develop symptoms. Symptoms could include diarrhea, fever, muscle pain, joint pain, headache, stiff neck, back pain, chills, sensitivity to bright light, and/or sore throat with fever and swollen glands. These symptoms can begin days to weeks after eating contaminated food.
Who is at risk of being affected by listeriosis?
The people most at risk of being affected by listeriosis include women who are pregnant, young children, adults over the age of 60, and people with weakened immune systems. Following some simple food safety guidelines can reduce the chance of getting and spreading listeriosis.
What precautions should I take to lower the chance of getting listeriosis?
To lower the chance of getting and spreading listeriosis and other food-borne illnesses all people can:
- Thoroughly cook raw foods from animal sources.
- Heat foods to steaming (at least 165°F / 74°C) to kill the bacteria.
- Do not drink unpasteurized milk (also called raw milk) or eat any foods made with unpasteurized milk, including cheese, yogurt and ice cream made from unpasteurized milk. Wash raw vegetables and fruit, even if you plan to peel them (remove skin).
- Separate uncooked meats from cooked meats and vegetables, especially with cutting boards to avoid cross-contamination.
- Wash hands, cutting boards, knives, counters, and sinks well after contact with uncooked foods with a new towel or paper towel.
- Avoid the ”Danger Zone” (temperatures within 40°F and 140°F) when storing food. Do not leave food out of the refrigerator for more than 2 hours.
- Consume ready-to-eat food as soon as possible.
- Keep your refrigerator at or below 40°F / 4°C.
- Clean your refrigerator regularly.
Women who are pregnant should take extra precautions to lower the chance of getting listeriosis:
- Do not eat soft cheeses (such as feta, Brie, Camembert, blue-veined cheeses, and Mexican-style cheeses such as queso blanco, queso fresco and Panela) unless they have labels stating that they are made from pasteurized milk. Note: some Mexican-style cheeses made from pasteurized milk have been a source of Listeria infections, possibly due to the cheese making process.
- Reheat any leftovers, ready-to-eat foods, hot dogs, cold cuts, deli meat, frozen vegetables, and frozen prepared foods to steaming (at least 165°F / 74°C),
- Prevent getting the juice of deli meats and hot dogs on other foods and surfaces. Wash your hands well after handling deli meats and hot dogs.
- Do not eat refrigerated hummus, pâté, meat spreads or refrigerated smoked seafood, unless it is an ingredient in a fully cooked dish (like a casserole).
- Avoid ready-to-eat salads.
How can I find out if I am infected with Listeria?
A blood test can confirm whether you have listeriosis. If you think you have listeriosis, talk with your healthcare providers.
I have listeriosis. Can it make it harder for me to become pregnant?
It is not known if listeriosis can make it harder to get pregnant.
Does having / getting listeriosis increase the chance of miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Listeriosis can increase the chance of miscarriage.
Does having / getting listeriosis increase the chance of birth defects?
Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at research studies to try to understand if an exposure, like listeriosis, might increase the chance of birth defects in a pregnancy. Based on the studies reviewed, it is not known if listeriosis increases the chance for birth defects above the background risk.
Would having / getting listeriosis increase the chance of other pregnancy-related problems?
Pregnancies affected by or exposed to Listeria can have an increased chance of infection in the uterus, preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces (2500 grams) at birth. Severe infection can increase the chance of stillbirth.
Listeriosis during pregnancy can also increase the chance for serious health problems after birth. Newborn babies infected with Listeria can develop either early-onset or late-onset listeriosis.
Early onset listeriosis develops 1 to 2 days after birth, and the baby often has signs of a serious bacterial infection.
Late-onset listeriosis occurs 1 to 2 weeks after birth and usually includes symptoms of meningitis (a condition that causes areas of swelling around the brain and spinal cord in the baby). If not treated quickly, meningitis can lead to long-term problems for some children. Late-onset listeriosis is most likely related to Listeria present in the mother’s birth canal.
Not all babies who are exposed to listeriosis during pregnancy will have problems.
How can I find out if my pregnancy has been affected by Listeria?
If you suspect you have been infected with Listeria, talk to your healthcare provider as soon as possible. Screening tests, such as ultrasounds have been used to check for an enlarged heart, thickened bowel, and increased thickness of the stomach walls, which might occur in some babies infected with Listeria. Diagnostic tests may also be available by testing amniotic fluid collected from amniocentesis, or by doing a blood test on the baby after birth. Discuss what options are available with your healthcare providers.
Does having / getting listeriosis in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if listeriosis can cause behavior or learning issues for the child.
Breastfeeding while I have listeriosis:
It is not clear if Listeria passes through breastmilk. If you have been diagnosed with listeriosis and are breastfeeding, talk to your healthcare provider or your child’s pediatrician. Be sure to talk to your healthcare provider about all of your breastfeeding questions.
If a man has listeriosis, can it affect his fertility or increase the chance of birth defects?
Studies have not been done to see if listeriosis could affect male fertility (ability to make healthy sperm) or increase the chance of birth defects. In general, exposures that men have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
Where can I find an updated list of listeria outbreaks?
The Centers for Disease Control and Prevention, better known as the CDC, has a list of all the outbreaks collected since 2011 in the United States. You can access a detailed list of new and previous outbreaks at: https://www.cdc.gov/listeria/outbreaks/index.html.
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