What are some foods that a pregnant woman should avoid to reduce the risk of listeriosis list at least five?

This sheet talks about exposure to or having Listeria infection (listeriosis) in a pregnancy and 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 Listeria monocytogenes bacteria, often called just Listeria. Listeriosis is typically caused by eating food that has been contaminated with Listeria. 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 which 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 degrees Fahrenheit or lower.

Some of the 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 occur in cantaloupes.

Who is at risk for listeriosis?

The people most at risk for 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 listeriosis.

What precautions should I take to avoid the infection?

To decrease the risk of listeriosis and other food-borne illness in all individuals:

• 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 at least 165°F (to steaming), to kill the bacterium.
• Wash raw vegetables and fruit, even if you plan to peel them (to remove skin).
• Separate uncooked meats from cooked meats and vegetables.
• Wash your hands, cutting boards, knives, counters, and sinks after contact with uncooked foods.
• Consume ready-to-eat foods as soon as possible.
• Keep your refrigerator at or below 40 degrees Fahrenheit (4 degrees Celsius).
• Clean your refrigerator regularly.

People who are pregnant should take additional precautions to decrease the risk of 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. However, it should be noted that some Mexican style cheeses made from pasteurized milk have been a source of Listeria infections, possibly due to the cheese making process.
• Reheat, to at least 165°F / to steaming, any leftovers, ready-to-eat foods, hot dogs, cold cuts, deli meat, frozen vegetables, and frozen prepared foods.
• Take care to not get the juice of deli meats and hot dogs on other foods/surfaces and wash your hands 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 affected with Listeria  will develop symptoms. Symptoms of listeriosis range from showing no symptoms to having 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. Be sure to discuss this with your healthcare provider.

How can I find out if my baby has been infected with Listeria during my pregnancy?

An ultrasound to look at the baby 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 increase the chance for miscarriage?

Miscarriage can occur in any pregnancy. There is an increased chance of miscarriage when infection 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 with a 3-5% chance of having a birth defect. This is called the background risk. Listeriosis infection has not been linked to an increased chance of birth defects.

Does Listeria cause other complications for pregnancy?

Pregnancies affected by or exposed to Listeria can have an increased chance of infection in the uterus, preterm delivery (delivery before 37 weeks of pregnancy) and in the most severe infection, the possibility of stillbirth.

Does having/getting listeriosis in pregnancy cause long-term problems?

Listeriosis during pregnancy can also increase the chance for serious health problems for the newborn. 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 where there are  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. Early diagnosis and treatment with high doses of antibiotics might prevent infection of the fetus.

Are there any treatments for listeriosis during pregnancy?

Large doses of antibiotics have been recommended to treat listeriosis during pregnancy. Such therapy has been successful, leading to lower incidences of preterm deliveries and stillbirths. Your healthcare providers will talk with you about the right treatment for your pregnancy.

Can I breastfeed with listeriosis?

It is not clear  if Listeria passes through breastmilk. It appears that if there is a chance, it is considered to be low. If you have been diagnosed with listeria and are breastfeeding, talk to your healthcare provider or your child’s pediatrician about this and all your breastfeeding questions.

I was exposed to Listeria. Can it make it harder for me to get my partner pregnant or increase the chance of birth defects?   

There is no evidence linking a father’s or sperm donor’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/pdf/.

Please click here for references.

OTIS/MotherToBaby recognizes that not all people identify as “men” or “women.” When using the term “mother,” we mean the source of the egg and/or uterus and by “father,” we mean the source of the sperm, regardless of the person’s gender identity.

View PDF Fact Sheet

Listeria infection is one of the most serious types of food poisoning. Pregnant women are 10–20 times more likely to get it than the general population. It can cause serious problems for you and your baby. Find out how to avoid it.

1. Listeria infection is caused by eating foods contaminated by Listeria monocytogenes bacteria. Foods most likely to be contaminated include ready-to-eat refrigerated meals and processed foods, eg, cooked and chilled meals, soft cheeses, cold meats, pâtés and smoked fish.
2. Listeria infection can be particularly dangerous for pregnant women. It can cause miscarriage, premature labour or stillbirth, and can also cause infection in your baby.
3. It's impossible to tell from the look, taste or smell whether food is contaminated with listeria. 
4. The best way to avoid listeria infection is to avoid high-risk foods and always follow food safety guidelines.
5. If you think you have eaten food contaminated with listeria or if you have any of the symptoms of listeria infection, contact your doctor or midwife right away. 

Foods to avoid when eating out or buying takeaways, Ministry for Primary Industries brochure, 2020

What is listeria infection?

Listeria infection is caused by eating food contaminated with bacteria called Listeria monocytogenes. It is one of the most serious types of food poisoning.Listeria bacteria are widely found in dust, soil, water, plants, sewage and animal droppings. Due to contamination, they have also been found in a variety of foods, including raw meat, raw vegetables and some processed foods.

Listeria infection is commonly transmitted to humans by eating contaminated food. The bug has been found in a variety of foods at all stages of preparation, from raw to well-cooked leftovers. Listeria can also grow on food stored in a fridge.

What are the symptoms of listeria infection?

The symptoms may be general, such as fever, headache, tiredness, aches and pains, which may be accompanied by runny poos (diarrhoea), feeling sick (nausea) and stomach cramps.

On average, symptoms appear after about 3 weeks but may appear as late as 2 months after you have eaten something with listeria. Many pregnant women do not have any symptoms. Even if you do not feel sick, you can pass the infection to your baby. 

How can listeria infection affect pregnant women?

Pregnant women are 10–20 times more likely to get listeria infection than the general population. Even a mild infection in a pregnant woman can cause miscarriage, stillbirth, premature birth or a baby who is very ill when born. 

How can listeria infection affect my baby?

Listeria can be passed from mother to baby during pregnancy or birth. Newborn babies infected with listeria may show signs of infection at birth or during the first few days of life. 

Infection in newborn babies can be very severe and can include lung infection (pneumonia) and meningitis. Infected babies may have severe difficulty with breathing and feeding.

What should I do if I think I have listeria infection?

If you think you have eaten food contaminated with listeria or if you have any of the symptoms of listeria infection, contact your doctor or midwife right away. Remember that it can take 2 months for symptoms to appear.

How is listeria infection treated?

Your doctor may ask for a blood test to see whether you have listeria infection. You may need to take antibiotics to treat the infection and prevent your baby from becoming infected.

How do I know if my food is contaminated?

Foods that are contaminated with listeria don't look, smell or taste off. Cooking and pasteurisation are the only ways to kill listeria. Listeria will continue to grow in foods in the fridge.

How can I prevent getting listeria infection?

The best way to avoid listeria infection is to avoid high-risk foods and always handle food safely.

High-risk foods that should be avoided

While food safety procedures aim to prevent listeria getting into the foods we eat, there are some foods that are more likely to be contaminated and pregnant women should not eat them.

Avoid all raw and under-cooked seafood, eggs, meat, and poultry while you are pregnant. Do not eat sushi made with raw fish (cooked sushi is safe). Cooking and pasteurisation are the only ways to kill listeria.

Foods that are safe to eat

• Most foods that have been thoroughly cooked (until piping hot) and eaten straight away.
• Vegetables and fruit that have been well washed.
• All tinned foods.
• Breads and cereals (without added mock creams or custards).
• Dried food (fruit, nuts, lentils, beans etc).
• Pasteurised milk and milk products, such as yoghurt, cheese etc.

Safe ways to handle food at home

Safe food handling and safe storage of food is important for everyone.

• Wash your hands before preparing food and between handling raw food and ready-to-eat foods.
• Wash raw fruit and vegetables well before eating.
• Cook all foods of animal origin, including eggs, thoroughly.
• Cook leftover foods or ready-to-eat foods, such as hot dogs, until steaming hot before eating.
• Keep uncooked meats separate from vegetables, cooked foods and ready-to-eat foods.
• Uncooked meats should also be well wrapped or covered.
• Wash hands, knives and cutting boards thoroughly with hot water and soap after handling uncooked foods.
• Take special care when using a microwave to heat food all the way through until it is piping hot.

Learn more

The NZ Government Ministry of Primary Industries (MPI) in Food Safety (previously called the NZFSA) has a booklet Food safety in pregnancy and other useful resources available to download from the Food safety website

You can also talk to your doctor or midwife and contact the Public Health Unit at your local Community Health Service.

References

Reviewed by

Dr Li-Wern Yim is a travel doctor with a background in general practice. She studied medicine at the University of Otago, and has a postgraduate diploma in travel medicine (Otago). She also studied tropical medicine in Uganda and Tanzania, and holds a diploma from the London School of Hygiene & Tropical Medicine. She currently works in clinical travel medicine in Auckland.