Listeriosis during pregnancy: what you should know

Listeriosis is a bacterial infection caused by bacteria Listeria monocytogenes. Although it is rare in healthy people, in risk groups such as pregnant women and people with weakened immune systems It can be very serious.

In this article, we tell you everything you need to know about listeriosis and pregnancy.

The listeriosis

Listeria infection or literiosis is a foodborne disease. It is the infection by a bacterium that normally lives in nature and that can cause Animals are carriers, in addition to polluting vegetables.

For these reasons, listeria can be found in:

  • Raw meats and fish
  • Fruits, vegetables and raw vegetables
  • Dairy products not pasteurized
  • Processed foods
  • Smoked fish

During pregnancy, you should avoid the consumption of raw foods where Listeria can live.

But nevertheless, cooking and pasteurization can kill the bacteria, therefore, risk groups are recommended to cook meat and vegetables and avoid the consumption of milk, cheese or other unpasteurized dairy products.

On the other hand, we must also bear in mind that listeria can appear even once the products are cooked. Indeed, may appear and infect them after cooking and before being packaged or consumed. Therefore, ready-to-eat foods (sausages, cold meats, cold meats) can also be potentially dangerous.

In addition, this bacterium is able to survive freezing and cooling, and It can be transmitted from the mother to the fetus, being highly dangerous for it. For this reason, it is essential that the mother maintain certain measures in order to avoid becoming infected.

We recommend you read: How to properly wash and disinfect vegetables and fruits

Types of listeriosis

Listeriosis is one of the most serious foodborne diseases, although fortunately it is rare (according to WHO, from 0.1 to 10 cases per year). However, despite the small number of cases, it has a high mortality rate. For this reason, its prevention is of the utmost importance.

There are two types of literiosis:

  • Non-invasive. It is a mild form of infection that causes febrile gastroenteritis due to listeria. It usually affects healthy people and, although it is not serious, it can be for risk groups, among which are pregnant women.
  • Invasive. This type of listeriosis is highly dangerous, with a mortality rate that can reach 20% or 30%. In fact, among its symptoms are fever, muscle pain, septicemia and even meningitis.

Regarding their respective incubation periods, in both cases usually one to two weeks. However, it can even extend to three months, so it can become really difficult to detect the infection in time.

Listeriosis and pregnancy

One of the main risks is spontaneous abortion or premature birth, so we must pay special attention to this risk group.

Listeriosis is especially dangerous during pregnancy, and not only for the mother. In fact, the infection can be transmitted to the fetus, which is especially vulnerable. In this way, it can cause:

  • Spontaneous abortion
  • Premature delivery
  • Infection of the fetus or newborn
  • Death of the fetus or newborn (approximately 22% of cases of perinatal listeriosis end in death of the fetus or neonate).

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As we mentioned earlier, the symptoms usually appear after having consumed the contaminated product. So, days later, among the symptoms may be observed:

  • Fever
  • Muscle pains
  • Vomiting
  • Sickness
  • Headache

The infection can appear during any time of pregnancy. But nevertheless, it is more normal to appear during the last quarter, since the mother's immune system may be slightly weakened.

In relation to the treatment, it is better to start it as soon as possible. In this sense, if symptoms occur, you should go immediately to the doctor who, through a simple blood test, can determine if you have listeria infection. From there, The treatment consists of antibiotics that, in addition, will help to prevent the infection of the fetus.


When cooking, we must take special care to avoid cross contamination between cooked and raw foods.

In general, the WHO proposes 5 keys for food safety:

  1. Keep clean. It is important to wash the products thoroughly, wash your hands before cooking, and keep the kitchen and refrigerator clean.
  2. Separate raw and cooked foods. That is, avoid cross contamination between them.
  3. Cook completely. It has been proven that cooking at more than 70 ° C contributes to the safety of food. However, we must bear in mind that some require special attention (for example, minced meat).
  4. Keep food at safe temperatures. For this, we should avoid leaving cooked food for more than two hours at room temperature. Also, we must not thaw them outside the refrigerator and, always, respect the expiration dates.
  5. Use water and safe raw materials. It is recommended to avoid processed and packaged foods.

In the case of listeria, since it can be found present in uncooked and unpasteurized foods, prevention measures will be aimed at avoiding the consumption of this type of products.

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

  • Avoid consuming unpasteurized milk and dairy products (including soft cheeses).
  • Heat cooked meats and processed meats (eg sausages) to at least 70 ºC before consuming them.
  • Avoid the consumption of smoked fish and meat.
  • Keep the leftovers in the refrigerator before they are more than two hours at room temperature. Also, consume them after, at most, 2 or 3 days.
  • Read product labels and follow the conservation guidelines.


In short, listeriosis is a rare infection, but we must not stop applying certain measures to avoid it. Further, in the case of pregnant women, special care must be taken, because the effects on the fetus could become mortal.

Hygiene measures must be maintained and processed meats and fish, unpasteurized dairy products and raw foods (especially meats, vegetables) must be avoided. Finally, just look at the symptoms, The pregnant woman should go to the doctor to start a treatment as soon as possible.