Listeriosis In Pregnancy: Symptoms, Causes, And Treatment

Listeriosis is one of the rarer infectious diseases. It is caused by the bacterium Listeria monocytogenes. Transmission occurs through contaminated food and close animal contact.

Here you can find out what you should look out for in your diet during pregnancy to avoid infection with this pathogen.

What Is Listeriosis?

Listeriosis is an infectious disease caused by bacteria. The pathogen, Listeria monocytogenes, belongs to a group of bacteria called listeria. Listeria can be transmitted to humans via contaminated food.

Healthy adults often feel little or nothing of the infection. However, flu-like symptoms can occur, such as fever, sore throat, conjunctivitis, vomiting and diarrhea.

In the case of listeriosis during pregnancy, there is a risk that the pathogen will infect the child via the umbilical cord or during birth, resulting in severe damage. Pregnant women and people with weakened immune systems often get infected with listeria and should therefore follow all precautionary measures regarding food selection and hygiene.

Overall, however, the infection is very rare: In 2016, there were 22 cases of listeriosis in pregnant women in Germany.

How Can Pregnant Women Become Infected With Listeria?

Infection occurs through consumption of animal and plant foods contaminated with listeria or through direct contact with infected animals. The most frequent cases occur in pregnant women with intact immune systems and without additional risk factors (HIV and Diabetes).

There are the following possibilities for the transmission of the pathogen from the mother to her child:

  • Via the placenta: this is the usual route of infection.
  • Via amniotic fluid that the newborn accidentally inhales at birth.
  • Via pathogens found in the vagina or anus, smear infection with Listeria can be caused.
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What Is The Course Of An Infection With Listeria?

In healthy adults, infection with Listeria usually has an inconspicuous or harmless course. Even during pregnancy, the symptoms are not very noticeable. However, flu-like symptoms such as fever and muscle pain occur, as well as vomiting and diarrhea.

In certain risk groups such as the elderly or immunocompromised and infants, fatal forms of the disease also occur. Pregnant women are at particularly high risk, as infection of the unborn child can cause severe damage and is fatal in about 30 percent of cases.

Why Is Listeriosis Particularly Risky In Pregnancy?

For pregnant women, infection with Listeria monocytogenes is a particular risk because infection of the unborn child can have serious consequences. Miscarriage, premature birth (typically with brown and cloudy amniotic fluid), stillbirth, or postpartum blood poisoning (sepsis) are common.

Neonatal Listeriosis (Early-onset Infection)

Neonatal listeriosis occurs during the 1st week of life and is therefore called early-onset infection. It may be manifested by the following symptoms:

  • Blood poisoning (sepsis)
  • Pneumonia
  • Skin lesions (granulomatosis infantiseptica)

The mortality rate is very high at 20 to 30%. Whether the newborn is infected can be tested with a blood, urine, or stool sample, as well as with a nasal or throat swab or by a cerebrospinal tap.

Late-onset Infection

Late-onset infection is when symptoms of illness do not appear for a few days to 4 weeks. In most cases, the infection manifests itself in the form of meningitis. In this case, the prognosis is much better than in the case of early-onset infection if appropriate therapy is given.

The infection leads to neurological sequelae and long-term complications in up to 20% of cases.

How Is Listeriosis Treated During Pregnancy And After Birth?

If you are diagnosed with listeriosis during pregnancy, you will be prescribed antibiotics for at least 2 weeks. In particular, high-dose amoxicillin or ampicillin will be used. The sooner you start treatment, the better the chances of preventing transmission of the pathogen to the unborn child.

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For children infected during birth or in the first weeks after birth, a three-week antibiotic therapy with. For treatment, the treating physician must choose a higher dose of the antibiotic than for non-pregnant patients so that it can penetrate the placenta.

The earlier the infection is detected and treated, the greater the chances for the mother not to lose the baby. If treated later, the risk for the child to become infected and suffer subsequent damage increases.

How Can I Recognize Listeriosis In Pregnancy?

With listeriosis in pregnancy, symptoms are often nonspecific and similar to those of the flu. In the pregnant woman, symptoms include fever, muscle aches, vomiting, and diarrhea.

If you observe these symptoms in yourself, you should immediately visit your doctor to have the cause clarified. The earlier the infection is detected, the greater the chances of preventing possible harm to the unborn child.

During pregnancy, the symptoms of a Listeria infection are often inconspicuous and can easily be overlooked. Flu-like symptoms can also occur with toxoplasmosis. Here, it is not bacteria that are the original cause, but a parasite (Toxoplasma gondii).

This infection can also have a harmful effect on the unborn child. A blood test can check whether you already have antibodies against toxoplasmosis and are therefore protected. The test also shows whether there is an acute infection.

How Can I Protect Myself Against Infection By Listeria?

There are no vaccinations against listeria yet. Gynecologists and obstetricians therefore recommend avoiding foods with a high risk of contamination. Unfortunately, you can’t tell if food is infested with listeria or not by its smell or appearance.

An infestation does not cause the food to spoil. Contamination of food with listeria can occur at various stages of extraction and processing. Listeria can also survive frozen.

Boiling, frying as well as pasteurization will kill listeria. However, this is only true if the temperature is 70 degrees for at least two minutes.

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You should observe the following rules when handling food:

  • Meat and fish dishes should be cooked completely through.
  • You should never eat minced meat raw.
  • Avoid products made from raw milk.
  • Avoid products made from raw meat.
  • Always remove the rind from cheese.
  • Observe the use-by date of perishable foods.
  • Always wash fruits, vegetables and herbs well before consumption.
  • Maintain consistent kitchen hygiene.
  • Keep food in the refrigerator for as short a time as possible.

The Federal Center for Nutrition provides an overview with information on what you can eat without hesitation to avoid listeriosis during pregnancy and what you should better not eat. You can download the flyer free of charge from the BZfE website.

Mozzarella In Pregnancy – What Is The Risk?

People are often warned against eating mozzarella during pregnancy. What is the risk of contracting listeria from mozzarella? Mozzarella is only a concern if it is made from raw milk, which is unpasteurized milk. Originally, mozzarella is a raw milk cheese made from buffalo milk.

Pregnant women must not eat this mozzarella because it may contain listeriosis pathogens. Mozzarella offered in supermarkets is usually made on the basis of pasteurized cow’s milk. Occasionally, however, buffalo mozzarella is also offered in the supermarket.

Please pay close attention to the labeling. According to food regulations, raw milk products must be clearly labeled. It is better to avoid raw mozzarella in restaurants or at private dinners because here you have no guarantee that it is not a raw milk product after all.

Mozzarella on pizza or other dishes from the oven is safe, because the germs are killed at high temperatures.

Toxoplasmosis In Pregnancy

Toxoplasmosis is an infectious disease caused by the parasite Toxoplasma gondii. This is spread especially by cat feces, raw meat and raw sausage, as well as by infected soil or sand.

Normally, the disease runs without symptoms and is therefore not even noticed. If the immune system is weakened, flu-like symptoms are also possible. During pregnancy, the infection can be dangerous for the unborn child.

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It is assumed that about 40 percent of all pregnant women have had an unnoticed toxoplasmosis infection at some point and have therefore developed antibodies against it. The antibodies protect them from reinfection. The baby is also safe from infection.

However, there is a danger for the unborn child if the pregnant woman is infected for the first time. Here, toxoplasmosis can be transmitted to the child. The risk of transmission depends on the time of infection and whether it is treated. It is estimated that about 1000 babies are infected in the womb in Germany every year.

The more advanced the pregnancy, the higher the risk of transmission from mother to child. On the other hand, the risk of the child becoming seriously ill then decreases.

The risk of damage to the child is higher the earlier in the course of pregnancy the initial infection occurs. The frequency of transmission of the infection to the child is then lowest.

Infection with toxoplasmosis can result in premature birth or stillbirth. Severe damage to the central nervous system occurs only in rare cases. Occasionally, eye disease can occur several years later. There is no vaccination against toxoplasmosis.

Toxoplamosis Prevention For Pregnant Cat Owners

  • Stop cleaning the litter box yourself or always wear plastic gloves and mouth guards.
  • Clean the litter box daily with water hotter than 70 degrees.
  • Place the litter box as far away from your living quarters as possible.
  • If possible, give your cat only dry and canned food during this time.
  • You can pet your cat, but you should always wash your hands afterwards.


Listeriosis during pregnancy carries a high risk for the unborn child. The best way to protect yourself from infection is to avoid all foods that pose a risk during pregnancy. Many of the measures mentioned are also suitable for preventing another infectious disease, toxoplasmosis.

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