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At your first prenatal visit, your health care provider likely talked with you about all the foods you should avoid during pregnancy — sushi, raw meat, deli meat and unpasteurized cheese — to prevent exposure to listeria. That's because consuming this bacteria can sometimes make you sick, and that extremely unlikely possibility becomes more likely when you're expecting.
Fortunately, there are steps you can take to greatly reduce your risk. Here's how, along with what happens if you think you've been exposed to listeria during pregnancy.
What is listeriosis?
Listeriosis is an illness caused by eating foods contaminated with the listeria monocytogenes bacteria. Keep in mind that simply being exposed to listeria, however, doesn't mean you'll develop an infection. In fact, most women who are exposed to listeria will not develop a listeriosis infection.
How common is listeriosis during pregnancy?
While the odds of being infected with listeriosis are still very, very low, it is significantly (13 times) higher during pregnancy — and the potential of its causing problems in pregnancy is higher.
What are the risks of listeriosis during pregnancy?
Listeria, unlike many other germs, enters the bloodstream directly and therefore can get to the baby quickly through the placenta (other food contaminants generally stay in the digestive tract). And an untreated infection can put baby at increased risk of more serious complications, including miscarriage, preterm labor, stillbirth or meningitis in newborns.
Listeriosis symptoms during pregnancy
Listeriosis can be hard to detect, partly because symptoms can develop up to two months after eating contaminated food and can vary from severe to mild. If you think you may have eaten food that contains listeria, watch for flu-like symptoms including:
- Fever over 100.6° F
- Muscle pain
- Backache
- Headache
- Gastrointestinal symptoms, including diarrhea
Note that you may have fever only, or you might not have any symptoms at all. So it's important to contact your doctor even if you think what you're experiencing might be caused by something else.
What to do if you think you've been exposed to listeria during pregnancy
Many moms-to-be worry about possible exposure to listeria, especially after big food recalls. In many cases, a watch-and-wait approach for symptoms is all that's necessary. Doctors will usually recommend testing if you have symptoms like a fever or gastrointestinal troubles.
If you're experiencing symptoms and your doctor suspects a listeriosis infection, he may order blood or other various tests to check for the bacteria and monitor your baby's health. If you have been infected, you'll get a prescription for antibiotics.
What should you do to protect yourself from listeria exposure during pregnancy?
One of the best ways to prevent listeriosis is to avoid foods that are most likely to be contaminated. These include:
- Hot dogs, lunch meats or cold cuts that are cold or heated lower than 165° F
- Refrigerated pâté and meat spreads
- Refrigerated, smoked seafood (like smoked salmon)
- Unpasteurized milk and soft cheeses (like feta, queso blanco, Brie and blue-veined cheeses)
- Unpasteurized fresh fruit juice and veggie juice (if you're not sure whether a juice has been pasteurized, don't drink it)
- Unwashed, raw produce
- Alfalfa and other sprouts
A few more tips to stay safe from listeria during pregnancy:
- Always wash produce (including those organic blueberries from the farmer's market) thoroughly in running tap water, even if you're planning to peel or cook it.
- As a precaution, even ready-cooked meats should be heated to steaming before eating.
- When eating out, watch for signs that the restaurant doesn't follow basic sanitation rules (and it should be pretty obvious): Perishable foods are kept at room temperature, the bathrooms are unclean, it's open season for flies, etc.
Unfortunately it's impossible to know for sure if the food you buy today will be recalled tomorrow — making it impossible to avoid listeria entirely.
That said, the risk of contracting the infection from day-to-day eating is extremely low, even if you are expecting. So try not to let worries about possible food contamination consume you.
Instead, spend your energy focusing on what you can do: Eat a balanced, healthy pregnancy diet to help support you and your growing baby.
- What to Expect When You’re Expecting, 5th Edition, Heidi Murkoff.
- The Centers for Disease Control and Prevention, Listeria (Listeriosis), December 2016
- National Institutes of Health, National Library of Medicine, Listeriosis in Pregnancy: Diagnosis, Treatment, and Prevention, 2008.
- American Congress of Obstetricians and Gynecologists, Management of Pregnant Women With Presumptive Exposure to Listeria monocytogenes, December 2014.
- Centers for Disease Control and Prevention, Listeria (Listeriosis) Questions and Answers, December 2016.
- Foodsafety.gov, Listeria, March 2019.
- U.S. Department of Health and Human Services, U.S. Food & Drug Administration, Food Safety for Pregnant Women, September 2011.
- American College of Obstetricians and Gynecologists, Listeria and Pregnancy, June 2018.
- National Institutes of Health, U.S. National Library of Medicine, MedlinePlus, Listeria Infections, April 2018.
Listeriosis is usually caught from eating food containing listeria bacteria.
You can get it from lots of types of food, but it's mainly a problem with:
These foods do not always cause listeriosis. If you have eaten them recently, you do not need to do anything unless you get symptoms of the infection.
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.
- 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.
- 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.
- It's impossible to tell from the look, taste or smell whether food is contaminated with listeria.
- The best way to avoid listeria infection is to avoid high-risk foods and always follow food safety guidelines.
- 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.
| High-risk foods that should be avoided: |
* Note that these foods are safe to eat if heated thoroughly to steaming hot (ie, above 72°C). |
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. |