This sheet is about having Listeria infection (listeriosis) in a pregnancy or while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.
What is listeriosis?
Listeriosis is an infection caused by the bacteria Listeria monocytogenes, often called just Listeria. Listeriosis is typically caused by eating food that has been contaminated with Listeria, particularly dairy products, leafy vegetables, fish and meats. Listeria can be found in your home, in restaurants, and other places such as the grocery store or 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, uncooked meat and fish, uncooked vegetables, lunch meat, and soft cheeses. Listeria outbreaks can also happen in cantaloupes.
Who is at risk for being affected by listeriosis?
The people most at risk for being affected by listeriosis include people 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 illness in all people:
- Do not drink unpasteurized milk (also called raw milk) or eat any foods made with unpasteurized milk.
- Thoroughly cook raw foods from animal sources.
- Heat foods to steaming (at least 165°F / 74°C) to kill the bacteria.
- Wash raw vegetables and fruit, even if you plan to peel them (remove skin).
- Separate uncooked meats from cooked meats and vegetables.
- Wash your hands, cutting boards, knives, counters, and sinks well after contact with uncooked foods.
- Consume ready-to-eat foods as soon as possible.
- Keep your refrigerator at or below 40°F / 4°C.
- Clean your refrigerator regularly.
People 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),
- Take care to not get the juice of deli meats and hot dogs on other foods / 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 do I know if I’ve been infected with Listeria?
Not everyone infected with Listeria will develop symptoms. Symptoms include diarrhea, fever, muscle pain, joint pain, headache, stiff neck, backache, 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. A blood test can confirm whether you have been infected with listeriosis. If you have eaten contaminated food and do not have symptoms, some experts feel no special testing or treatment is needed. If you think you have listeriosis, talk with your healthcare provider.
I have listeriosis. Can it make it harder for me to get pregnant?
It is not known if listeriosis can make it harder to get pregnant.
Does having / getting listeriosis increase the chance for miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. There is an increased chance of miscarriage when listeriosis occurs in the first trimester of pregnancy. Infections after the first trimester are associated with a lower chance of pregnancy loss.
Does having / getting listeriosis increase the chance of birth defects?
Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Based on the studies reviewed, it is not known if listeriosis increases the chance for birth defects above the background risk.
Does 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 1-2 days after birth, and the baby often has signs of a serious bacterial infection. Late onset listeriosis occurs 1-2 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 with antibiotics, the effects of 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?
An ultrasound can be used to check for an enlarged heart, thickened bowel, and increased thickness of the stomach walls, which may occur in some babies infected with Listeria. A blood test can also be performed on the baby after birth to detect whether the baby has been infected with Listeria.
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 having listeriosis:
It is not clear if Listeria passes through breastmilk. If there is a chance, it is considered to be low. 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 male has listeriosis, could it affect fertility (ability to get partner pregnant) or increase the chance of birth defects?
Studies have not been done to see if listeriosis could affect male fertility or increase the chance of birth defects above the background risk. There is no evidence linking a male’s exposure to Listeria with a higher chance of infection during pregnancy. In general, exposures that fathers and sperm donors 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/.
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OTIS/MotherToBaby encourages inclusive and person-centered language. While our name still contains a reference to mothers, we are updating our resources with more inclusive terms. Use of the term mother or maternal refers to a person who is pregnant. Use of the term father or paternal refers to a person who contributes sperm.