Is it easy to get Listeria when pregnant?

Pregnant women are told time and again: Don’t eat raw meat, avoid unpasteurized cheese, steer clear of deli counter salads. Why? You can largely blame listeriosis, a foodborne illness that doesn’t pose much risk for mom but can be harmful for baby. Find out what causes listeriosis, what your odds are of contracting it and the steps you can take to prevent it.

Technically speaking, listeriosis is an infection caused by Listeria monocytogenes bacteria. Practically speaking, listeriosis is a type of food poisoning that can cause pregnancy complications.

Listeria bacteria are found in soil, water and sewage, but they can also contaminate food—so if you eat something that’s been contaminated with listeria, you can develop listeriosis. The listeria bacteria is killed with heating and pasteurization, so listeriosis is usually linked to eating uncooked meats or vegetables, raw or unpasteurized milk products, or processed foods [such as hot dogs and deli meat] that become contaminated after being cooked at the food processing facility.

Listeriosis can make people feel sick, but rarely causes severe health problems. What’s scary for moms-to-be, however, is that having it during pregnancy increases the risk of miscarriage, stillbirth and preterm birth. Babies of moms who had listeriosis during pregnancy are also at risk for listeria infection.

How Common Is Listeriosis During Pregnancy?

Wondering what are the odds of getting listeriosis while pregnant? Good news—they’re very low. It’s true that pregnant women have an increased risk of contracting listeriosis, but the real risk is still tiny. According to the Centers for Disease Control and Prevention [CDC], there are approximately 1,600 cases of listeriosis in the United States each year. But only about one in seven cases—or about 200 cases per year—occur in pregnant women, out of nearly 4 million pregnancies every year.

“You’re much more likely to step outside and slip on ice on your front steps in the winter than you are to contract listeria,” says Kelly Kasper, MD, ob-gyn and associate clinical professor at the Indiana University School of Medicine. And if you do get listeria, baby might not— transmission of listeriosis from mom to baby is not a sure thing. Plus, listeria infections are easily treatable with antibiotics.

How Do You Know If You Have Listeriosis?

“The symptoms of a listeria infection look a lot like a cold or mild flu,” Kasper says. “The most common symptom is a fever. You might also have muscle aches or a sore throat.” Some people also have diarrhea.

Because the symptoms are so nonspecific, it’s impossible to tell if you have listeriosis solely based on symptoms. That’s why doctors tell pregnant women to contact their health care provider if they’re running a fever—not because they’re always worried about listeriosis, but because fever is a symptom of all kinds of ailments, many of which should be diagnosed and treated right away. The only way to figure out if your symptoms pose a threat to you or baby is to have them checked out by a qualified health care provider.

So how do you test for listeria in pregnancy? If your doctor suspects listeriosis—if you have symptoms of listeriosis and have recently eaten some suspect food, for instance—she can order a simple blood test to determine if you have listeriosis or not.

How Does Listeriosis Affect Baby?

Listeriosis increases the risk of miscarriage, stillbirth, preterm delivery and listeriosis infection once baby is born, but the odds of anything bad happening to baby are slim. Here’s why:

• Listeria infection can spread from mom to baby through the placenta, but it’s not a sure thing. So even if you get listeriosis, baby might not. The antibiotics used to treat listeriosis during pregnancy can prevent infection of the fetus.

• Antibiotics can also be used to treat [and prevent complications of] listeriosis in newborns. While listeriosis in babies can cause severe blood infections, meningitis, pneumonia and even death, treatment with antibiotics can resolve the infection and usually prevent complications.

How To Prevent Listeriosis During Pregnancy

If you want to decrease your risk of getting listeriosis to almost zero, you can follow the official listeriosis prevention guidelines and avoid eating the following during pregnancy:

• Unpasteurized soft cheeses
• Refrigerated smoked seafood
• Raw or unpasteurized milk products
• Cold [or room temp] deli meats or hot dogs [they’re fine if they’re heated to steaming hot]
• Prepared deli counter salads, such as egg salad, tuna salad and seafood salad

Or you can take a slightly more relaxed approach. Given the extreme improbability of contracting listeriosis from properly handled foods, Kasper suggests eating food you’ve prepared yourself and following common sense guidelines when you prep and store it:

• Store foods safely. Make sure your refrigerator is set to 40 degrees Fahrenheit or below, and return items to the fridge as soon as possible after using. Don’t let foods sit out for long periods at room temperature.

• Wash fruits and vegetables. Rinse any raw produce thoroughly under running tap water before eating.

• Pay attention to expiration dates. If your lunch meat is past its expiration date [or if it smells or looks funny], throw it away.  

“You want to be smart about listeria and keep yourself healthy. But at the same time, you don’t want to quit living,” Kasper says. “There are some things that we know are very important, common and threatening to a pregnancy, like influenza—that’s why we recommend the flu shot. Listeriosis is very uncommon. You don’t have to put yourself in a plastic bubble because you’re afraid of what might happen.”

What do you do if you have listeriosis? Oral antibiotics can effectively treat listeriosis during pregnancy. Taking the antibiotics can help baby as well. Research shows that treating moms-to-be with high doses of antibiotics during pregnancy decreases the incidence of listeriosis-related preterm births and stillbirths.

Stories From Moms-To-Be Who Have Had Listeriosis

“I know it’s rare but my doula ate a sub and she got so sick from listeriosis she went into labor. Thankfully she was full term. My OB is very strict about [sticking to safe foods]. That says something about the potential dangers. Something to keep in mind—to me [eating certain foods is] not worth the risk.”

“A friend of mine had listeriosis during her first pregnancy—the baby was okay!—and from what she told me, it was constant, uncontrollable vomiting. She said she was puking every five minutes, for a good hour or so. Poor thing!”

“A woman who goes to my OB practice did get listeriosis while I was pregnant with my first child and it did not have a good outcome. Even the doctors in the practice were shocked because it is so rare.”

Expert source: Kelly Kasper, MD, ob-gyn and associate clinical professor at the Indiana University School of Medicine.

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.

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

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