Listeriosis during Pregnancy: What You Should Know

Eating raw, uncooked foods can cause listeriosis or listeria infection. For this reason, pregnant women should always try to cook foods and opt for pasteurized dairy products. In this article, discover what you should know about listeriosis during pregnancy.
Listeriosis during Pregnancy: What You Should Know

Last update: 21 October, 2019

Listeriosis is a bacterial infection caused by the bacterium Listeria monocytogenes. Although it’s rare in healthy individuals, it can be really serious in risk groups such as pregnant women and people with weakened immune systems.

In this article, we’ll tell you everything you need to know about listeriosis during pregnancy.


Listeria infection or listeriosis is a foodborne illness. It’s an infection caused by a bacterium that normally lives in nature and may come from animal carriers in addition to contaminated vegetables.

For these reasons, you can find Listeria in:

  • Raw meat and fish
  • Fruits, greens, and raw vegetables
  • Unpasteurized dairy products
  • Processed foods
  • Smoked fish
A raw steak.

During pregnancy, you should avoid consuming raw foods that may contain Listeria.

However, cooking and pasteurization can kill the bacteria, which is why experts recommend risk groups to cook meats and vegetables and avoid consuming milk, cheese, and other unpasteurized dairy products.

Moreover, you must also consider that Listeria may infect foods even after they’re cooked and packaged. Thus, foods that are ready for consumption (such as sausages, cold meats, or cold cuts) can also be potentially dangerous.

Also, this bacterium can survive freezing and refrigeration and can be spread from mother to fetus. It’s very dangerous for fetuses and newborns. For this reason, the soon-to-be mother needs to apply certain measures to avoid becoming infected.

Types of listeriosis

Although listeriosis is one of the most severe foodborne illnesses, fortunately, it’s quite rare (according to the World Health Organization, there are 0.1 to 10 cases per million people per year). However, despite the small number of cases, it has a high mortality rate. For this reason, prevention is crucial.

There are two types of listeriosis:

  • Non-invasive. This is a mild form of the disease that causes febrile listerial gastroenteritis. It usually affects healthy people. Although it’s not severe, it may be so for risk groups, including pregnant women.
  • Invasive. This type of listeriosis is highly dangerous, with a mortality rate of 20 to 30%. In fact, some of its symptoms include fever, muscle pain, sepsis, and even meningitis.

As for their incubation periods, it’s usually of one to two weeks in both types. However, it may even extend to three months, which is why it can be really difficult to detect the infection early.

Listeriosis during pregnancy

A pregnant woman with nausea because of listeriosis during pregnancy

One of the main risks is miscarriage or preterm labor, which is why experts pay special attention to this risk group.

Listeriosis during pregnancy is very dangerous, and not only for the mother. In fact, the pregnant mother can spread the infection to the fetus, which is especially vulnerable. Thus, it can cause:

  • Miscarriage.
  • Preterm labor.
  • Infection of the fetus or newborn.
  • Death of the fetus or newborn (approximately 22% of perinatal listeriosis cases result in the death of the fetus or newborn).

As we mentioned above, the symptoms usually manifest after consuming the contaminated product. Therefore, you can observe the following symptoms a few days later:

  • Fever
  • Muscle aches
  • Vomiting
  • Nausea
  • Headache

Infection can occur at any time during pregnancy. However, it’s more likely in the last trimester, since the woman’s immune system may be slightly weakened.

Regarding treatment, it’s better to start as soon as possible. In this sense, if symptoms manifest, you must go see your doctor immediately. Through a simple blood test, they may determine if you’re suffering from listeriosis. From that point on, the treatment consists of antibiotics that will also help prevent infection of the fetus.

Prevention of listeriosis during pregnancy

A pregnant woman cutting vegetables.

When you’re cooking, you must be really careful to avoid cross-contamination between cooked and raw foods.

The WHO proposes five keys to safer food:

  1. Keep clean. It’s important to thoroughly wash products, wash your hands before cooking, and keep your kitchen and refrigerator clean.
  2. Separate raw and cooked foods. This way, you prevent cross-contamination between them.
  3. Cook thoroughly. Cooking foods over 158°F contributes to food safety. However, you must consider that some foods require special attention (such as minced meat).
  4. Keep food at safe temperatures. To do this, you must avoid leaving cooked foods at room temperature for more than two hours. Also, you shouldn’t thaw foods out of the refrigerator and always respect expiration dates.
  5. Use safe water and raw materials. Experts recommend avoiding processed and packaged foods.

Since Listeria can infect uncooked and unpasteurized foods, prevention measures should be aimed at avoiding the consumption of these products.

Thus, in addition to the above measures, pregnant women should:

  • Avoid consuming unpasteurized milk and dairy products (including soft cheeses).
  • Heat cold cuts and processed meats (such as sausages) to at least 158°F before consuming.
  • Avoid eating smoked fish and meat.
  • Store leftovers in the refrigerator before they’ve been out at room temperature for more than two hours. Moreover, they should consume them, at most, for the next two to three days.
  • Read product labels and follow conservation guidelines.


Although listeriosis during pregnancy is rare, you must apply certain measures to prevent it. Also, pregnant women should be especially careful because it could have deadly consequences for the fetus.

Pregnant women should maintain proper hygiene and avoid processed meats and fish, unpasteurized milk and dairy products, and raw foods (especially meats and vegetables). Finally, pregnant women should see a doctor as soon as they start noticing symptoms to start treatment as soon as possible.

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