How Listeriosis Can Affect Pregnancy

Listeriosis is a disease caused by a bacterium of the genus Listeria. Generally, the disease isn't serious except in risk groups, such as pregnant women or the elderly. In this article, discover how listeriosis can affect pregnancy.
How Listeriosis Can Affect Pregnancy
Olga Carbajo

Written and verified by the biologist Olga Carbajo.

Last update: 27 December, 2022

Recently, as a result of poor food processing, Spain registered an outbreak of listeriosis. In Spain, many people were infected. In this article, you’ll discover how listeriosis can affect pregnancy.

Microorganisms infect people equally, regardless of their age or sex. Thus, our physical conditions make a difference in the infectious process. How the infection affects you and the repercussions it may have depend on your state of health.

What’s listeriosis? Effects on pregnancy

Listeriosis is a disease that the bacteria Listeria monocytogenes causes. People catch it by consuming foods that became infected by said bacteria during processing. However, it can also be found in water or on soil.

Unpasteurized milk or poorly processed foods are some of the raw products that can be infected by it. The current outbreak in Spain originated in a processed meat food company and, of course, will affect anyone who consumes a contaminated product.

How Listeriosis Can Affect Pregnancy

You can confuse the first symptoms of this condition with food poisoning caused by other microorganisms such as salmonella, since they both cause:

  • Fever and chills.
  • Headache.
  • Stomach ache.
  • Vomiting.
  • Diarrhea (rarely).

And although antibiotics can easily fight the disease, the Centers for Disease Control and Prevention (CDC) warn of possible complications in the following risk groups: the elderly, people with weakened immune systems, pregnant women, and unborn babies.

How listeriosis can affect pregnancy

It should be noted that, as in any infectious process, not stopping the advance of the microbe in time can allow it to invade other organs outside the intestines. The parasite could cross the blood-brain barrier and cause meningitis. In addition, it can also cross the placental barrier.

In the case of pregnant women, the infection can reach the baby and can cause from a miscarriage and preterm delivery to infections in the newborn, where the consequences can be irreversible and even fatal.

However, this shouldn’t alarm the population. Microbiologist Rafael Cantón, spokesman for the Spanish Society of Infectious Diseases and Clinical Microbiology, states that everyone should remain calm. As a general rule, the only symptoms pregnant women have are fever, tiredness, and muscle aches, apart from those related to the gastrointestinal process.

Development of the disease

Symptoms can manifest immediately after consuming a contaminated food or up to 70 days after eating it. However, it’s normal for invasive listeriosis to have an incubation period of one to four weeks prior to the development of the disease.

How Listeriosis Can Affect Pregnancy

If the pregnancy is in the third trimester, it’s likely that listeriosis won’t affect the pregnancy. It’s usually asymptomatic or resembles a flu-like process, as long as you treat it. At another time of the pregnancy, and once the maternal-fetal barrier has been crossed, an intrauterine infection will occur due to sepsis.

Similarly, it can spread to the newborn during delivery. In these cases, severe listeriosis can cause meningitis, encephalitis, or headaches if the newborn’s central nervous system has been affected. Early detection and timely delivery of antibiotics should avoid such complications.

Tips to avoid infection

As you can find the bacteria in both contaminated water and soils, the CDC recommends people to properly wash vegetables or produce before consumption. Also, it urges pregnant women to cook meat well to avoid possible infections and to make sure that the pregnancy isn’t compromised.

Likewise, they should avoid consuming foods made with unpasteurized milk, such as fresh milk cheeses or yogurts, as these derivatives can carry the bacteria. This is because manufacturers don’t subject them to high temperatures to eliminate microbes.

If you suspect that you may have contracted the disease, we advise you to seek medical attention as soon as possible and inform a doctor that you possibly ate contaminated food, even if several weeks have passed. Early diagnosis will avoid major consequences.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Medline. (31 julio 2019). Listerioris [artículo web especializada]. Recuperado de:
  • CDC. (29 junio 2017). Listeria monocytogenes [artículo en web especializada]. Recuperado de:
  • Montojo M. (20 agosto 2019). Entrevista a Rafael Cantón. Recuperado de:

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.