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Infections Call your provider

Listeriosis in pregnancy

Also known as Listeria infection, Listeria in pregnancy. Any time, most often the third trimester.

Listeriosis is a foodborne infection caused by the bacterium Listeria, and it is one reason your provider hands you that list of foods to avoid. The key contrast: in you it is usually mild, a flu-like illness or no symptoms at all, but it can cross the placenta and be devastating for your baby, causing miscarriage, stillbirth, or serious newborn illness. It is largely preventable through food choices, and when it does occur, prompt antibiotics protect the baby.

Know the warning signs When to call a provider
How common
About 1 in 25,000
Pregnancies per year in the US; pregnant people are far more susceptible than others.
When
Most often third trimester
Can occur any time; symptoms may start up to two months after exposure.
Urgency
Act on fever
Mild in the mother but serious for the baby; prompt antibiotics matter.
Outlook
Preventable, treatable
Food safety prevents most cases; early antibiotics protect the baby.

Understanding it

What is listeriosis in pregnancy?

Listeriosis is an infection with the bacterium Listeria monocytogenes, caught from contaminated food. What sets it apart is the mismatch between you and your baby: for you, usually a mild, flu-like illness, fever, chills, muscle aches, sometimes nothing at all; for the baby, potentially severe, because the bacteria can cross the placenta.

The numbers explain the concern. Pregnancy softens the immune defenses that hold this organism in check, so pregnant people are roughly ten times likelier than others to get it. And once it reaches a pregnancy it is dangerous, threatening miscarriage, stillbirth, preterm birth, and life-threatening newborn illness like blood infection or meningitis.

Listeria grows even at refrigerator temperatures and survives freezing, which is why chilled ready-to-eat foods, deli meats, soft cheeses, refrigerated smoked fish, are the classic culprits. Symptoms usually appear within two weeks of the contaminated meal but can take up to two months, making the source hard to pin down.

Two things matter most: prevention through food choices, and prompt treatment, which works early. Avoiding the high-risk foods, and heating deli meats and hot dogs until steaming, prevents most cases. If you develop a fever or suspect an exposure, call so your provider can test and, if needed, start high-dose antibiotics that cross the placenta. A fever in pregnancy is never something to wait out.

Symptoms

What are the symptoms?

In the mother, listeriosis is usually mild and flu-like, or silent. The seriousness is for the baby. A fever in pregnancy, or symptoms after a possible exposure, warrants a call.

Early signs

  • Fever and chills
  • Muscle aches
  • Headache
  • Nausea, vomiting, or diarrhea
  • Sometimes no symptoms at all, despite the baby being at risk

Emergency signs — call 911

  • A high fever, a very bad headache, a stiff neck, or confusion, which can signal the infection has spread to the brain: seek emergency care
  • Fever in pregnancy after eating a high-risk food or a food later recalled for Listeria
  • Reduced fetal movement
  • Signs of preterm labor: regular contractions or your water breaking

Why it matters

Risks to you and baby

Pregnancy loss

The gravest risk. Listeriosis can cause miscarriage or stillbirth, and about 1 in 4 who get it lose the pregnancy or their baby shortly after birth. This is why it is treated so urgently.

Severe newborn infection

A baby infected before or during birth can develop blood infection (sepsis) or meningitis, which can cause lasting harm or death. Antibiotics given to the mother before delivery lower this risk.

Preterm birth

Listeriosis frequently leads to premature delivery, with about half of affected pregnancies delivering preterm, adding the risks of prematurity to those of the infection.

Usually mild for the mother

For you, it is typically a mild, flu-like illness. The danger is overwhelmingly to the baby, which is why a seemingly minor illness is taken seriously in pregnancy.

How it's found

How is it diagnosed?

Listeriosis is diagnosed by growing the bacteria from a blood culture. It is considered when a pregnant person has a fever, especially after a possible exposure.

Blood culture

The definitive test. Blood is cultured to grow and identify Listeria; at least two sets are taken because cultures are positive in up to about half of invasive cases.

Clinical suspicion after exposure

A fever with flu-like symptoms in pregnancy, particularly after eating a high-risk or recalled food, prompts testing and, often, starting antibiotics before results return.

Spinal fluid test if needed

If meningitis is suspected, from a stiff neck, severe headache, or confusion, spinal fluid is tested for infection of the brain and its lining.

Whenever a pregnant person has an unexplained fever, and especially after a known or suspected Listeria exposure or food recall.

Treatment

How is it managed?

Listeriosis is treated with prompt, high-dose intravenous antibiotics that cross the placenta to protect the baby. Early treatment clearly improves the outcome.

Treatment paths

First-line treatment is high-dose intravenous ampicillin, started promptly, sometimes before culture results return if suspicion is high, because early treatment improves newborn outcomes. Gentamicin is sometimes added. For a true penicillin allergy, trimethoprim-sulfamethoxazole is the usual alternative. Treatment continues for at least three weeks in pregnancy.

Monitoring

The baby is watched closely during and after treatment, and the newborn is evaluated and treated at any sign of infection.

Can it recur?

Listeriosis is caught from food, not a condition that recurs from pregnancy to pregnancy, so having had it does not make it likelier next time. Protection comes from food safety, the same in every pregnancy, not from anything about a prior infection.

What you can do

Can it be prevented?

  • Avoid the high-risk foods

    Skip unheated deli meats, hot dogs, and cold cuts; refrigerated pâté and meat spreads; soft cheeses made from unpasteurized milk (queso fresco, brie, camembert, blue cheese); raw milk and anything made from it; raw sprouts; and refrigerated smoked seafood.

  • Heat deli meats and hot dogs until steaming

    If you do eat deli meats or hot dogs, heat them to steaming, about 165 F, which kills Listeria. Eat them right after heating, not cold.

  • Wash produce and handle food safely

    Wash fresh fruits and vegetables well, avoid cut melon left out more than two hours, keep your refrigerator clean, and use perishable foods promptly, since Listeria grows even when chilled.

  • Pay attention to food recalls

    Listeria outbreaks and recalls are common. If you have eaten a recalled food and develop a fever, tell your provider so you can be evaluated and treated early.

Who is more at risk

Risk factors

Pregnancy itself
Pregnancy is the dominant risk factor, leaving you far more susceptible than other healthy adults because of its immune changes.
Eating high-risk foods
Unpasteurized dairy, deli meats, soft cheeses, refrigerated smoked fish, raw sprouts, and unwashed produce are the exposures that lead to infection, and they are largely avoidable.
Food recalls and outbreaks
Eating a food that is later recalled for Listeria contamination is a specific exposure worth acting on if symptoms follow.
Later pregnancy
Listeriosis occurs most often in the third trimester, though it can happen at any stage.

Do not wait

When to call your provider or 911

  • Seek emergency care for a high fever, a very bad headache, a stiff neck, or confusion, which can mean the infection has spread to the brain.
  • Call your provider promptly for any fever in pregnancy, especially after eating a high-risk or recalled food.
  • Report symptoms like chills, muscle aches, or an upset stomach after a possible Listeria exposure.
  • Seek care for reduced fetal movement or signs of preterm labor.
  • Tell your provider if you have eaten a food that is later recalled for Listeria, even if you feel well.

Talking to your team

Questions to ask your provider

  • Which foods should I avoid to lower my Listeria risk?
  • I ate a food that was recalled; what should I watch for or do?
  • I have a fever. Could this be listeriosis, and should I be tested?
  • If I need treatment, which antibiotic is used, and for how long?
  • How will my baby be monitored if I have listeriosis?
  • Is it safe to heat deli meats, and how hot do they need to be?

Keep reading

More on listeriosis in pregnancy

All pregnancy guides articles

Good to Know

Listeriosis in pregnancy FAQs

Common questions about listeriosis in pregnancy, answered.

Why is Listeria such a big deal in pregnancy?

Because of a dangerous mismatch: usually mild or silent for you, but able to cross the placenta and turn severe for your baby, causing miscarriage, stillbirth, or life-threatening newborn illness. Easy to catch, mild in you, devastating for the baby: that is why it gets so much attention.

Which foods should I avoid?

The main ones are unheated deli meats, hot dogs, and cold cuts; refrigerated pâté and meat spreads; soft cheeses made from unpasteurized milk like queso fresco, brie, camembert, and blue cheese; raw (unpasteurized) milk and anything made from it; raw sprouts; refrigerated smoked seafood; and unwashed produce or cut melon left out too long. Heating deli meats and hot dogs until steaming makes them safe.

I ate deli meat before I knew. Should I worry?

Try not to panic. Most exposures do not lead to infection. Going forward, avoid the high-risk foods or heat deli meats until steaming. Mainly, watch for symptoms: if a fever or flu-like illness develops over the next several weeks, or you learn the food was recalled, tell your provider so you can be tested and treated early.

Can I still eat cheese and lunch meat during pregnancy?

Some, yes. Hard and pasteurized cheeses are fine; it is specifically soft cheeses made from unpasteurized milk to avoid. Deli meats and hot dogs are safe heated until steaming, about 165 F, and eaten right away rather than cold.

How is listeriosis treated?

With prompt, high-dose intravenous antibiotics, usually ampicillin, that cross the placenta to protect your baby. If suspicion is high, treatment may start before culture results return. For a true penicillin allergy, a different antibiotic is used. Treatment runs at least three weeks in pregnancy.

Why does Listeria survive in the fridge?

Listeria grows at refrigerator temperatures and survives freezing, unlike most food bacteria that cold slows down. That is why chilled, ready-to-eat foods like deli meats and soft cheeses are the classic sources, and why keeping your fridge clean and using perishables promptly matters.

How long after eating do symptoms appear?

It varies. Symptoms usually start within two weeks of the contaminated meal but can take up to two months. That long, variable window is part of why the source is hard to identify, and why a fever weeks after a possible exposure is worth mentioning.

Will it happen again in my next pregnancy?

Not from having had it before. Listeriosis is caught from contaminated food, not a condition that recurs from one pregnancy to the next, so a prior infection does not make you likelier to get it again. Your protection in every pregnancy comes from the same food-safety steps.

Medically Reviewed · Updated

Reviewed by Dr. Grace Lin, MD, FACOG · OB-GYN

Obstetrician-gynecologist focused on reproductive and sexual health for women: pregnancy, BV, yeast, trichomoniasis and HPV/cervical screening. Our editorial guidelines →

6 Sources

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