How do you know if you have Listeria when pregnant?

What is listeriosis?

Listeriosis is a serious infection that you can get by eating food contaminated with the bacterium Listeria monocytogenes.

Pregnant women and their developing babies as well as newborns, people with weakened immune systems, and the elderly are particularly susceptible to listeria infection. In fact, pregnant women are 10 times more likely than others to get listeriosis. Hispanic pregnant women face an even greater risk, and are 24 times more likely to get listeriosis.

The primary threat for a pregnant woman is the devastating effect that listeriosis may have on her pregnancy and her baby.

Fortunately, the illness is rare: The Centers for Disease Control and Prevention (CDC) estimates that about 1,600 people contract listeriosis in the United States every year. About a sixth of reported cases occur in pregnant women.

Listeria symptoms

Symptoms of listeriosis may appear a week to a month after eating contaminated food, or they may not show up for a couple of months. Many pregnant women have no listeria symptoms or only mild, flu-like symptoms if they become infected. Even without symptoms, you can pass the bacteria on to your baby.

Listeriosis symptoms can include:

• Fever
• Fatigue
• Muscle aches
• Upset stomach or diarrhea
• Stiff neck
• Headache
• Confusion

Call your healthcare practitioner immediately if you have any symptoms of listeriosis.

How could listeriosis affect me and my baby?

Unless you have an underlying disease that impacts your immune system, it's unlikely for listeriosis to seriously affect your health during pregnancy. (Some pregnant women who have listeriosis suffer from dehydration due to vomiting and diarrhea but this is uncommon.)

However, the infection can have grave consequences for your developing baby, especially if you're not treated promptly.

Listeria can infect the placenta, the amniotic fluid, and the baby, and can cause miscarriage or stillbirth. Infected babies who survive are likely to be born prematurely. Many will be born severely ill or get sick soon after birth, with problems that can include blood infection, difficulty breathing, fever, skin sores, lesions on multiple organs, and central nervous system infections such as meningitis. Some infected babies will die or suffer long-term consequences, such as intellectual disability; paralysis; seizures; blindness; or brain, kidney, or heart problems.

Some newborns of infected mothers appear healthy at birth but show signs of infection, usually meningitis, a week or even several weeks after delivery. This so-called "late-onset listeriosis" may be the result of a baby becoming infected during labor and birth (an infected woman may harbor the bacteria in her cervix, vagina, or gastrointestinal tract).

Not all babies who are born to a mom infected with listeriosis while pregnant will have problems. If the mom is treated with antibiotics during pregnancy, the baby may avoid infection.

How is listeriosis managed?

Your caregiver will give you a blood test to confirm that you have listeriosis. If it's positive, you'll be given IV antibiotics, which will treat your infection and may help protect your baby.

Ultrasounds will be done to check for problems and to see how your baby is growing.

After birth, your baby can be given a blood test to see if she's infected with Listeria. If she is, she'll be given antibiotics, too.

How to avoid food poisoning while pregnant

To avoid getting infected with listeria and other foodborne bacteria and viruses, follow these guidelines when choosing, storing, and preparing food:

Avoid unsafe foods

You can't tell if a food is harboring Listeria by looking at it or smelling it. So it's important for pregnant women to be aware of the foods that are most likely to be contaminated and avoid them. Steer clear of:

• Deli meats, unless you heat them. Don't eat cold cuts or deli meat, refrigerated pâtés or meat spreads, or refrigerated smoked or pickled fish unless they're cooked until steaming hot (say, on a pizza or in a hot sandwich). And even though hot dogs are precooked, be sure to cook them until they're steaming hot as well. Canned or shelf-stable products that don't need to be refrigerated should be fine to eat.
• Cold smoked fish that isn't shelf stable. It's okay to eat canned and shelf-stable tuna, salmon, and other fish. But cold smoked fish that isn't shelf stable (it will be labeled "Keep refrigerated") isn't safe unless cooked (in a casserole, for example). These items are often found at deli or seafood counters and may be labeled "nova-style," "lox," "kippered," or "smoked."
• Prepared salads and wraps. Stay away from prepared salads from delis and supermarkets, especially those containing eggs, chicken, or seafood. (Even vegetable salads can harbor Listeria, though.) Also, skip potato salad that's not on ice at a picnic and meat that's not kept steaming hot at a buffet. Unless you're positive that the food has been safely prepared and has been sitting out for less than two hours one hour on a very warm day it's not worth the risk.
• Unpasteurized (raw) milk. That includes both raw milk and raw-milk cheeses. Don't eat soft cheese such as feta, Brie, or Camembert; blue-veined cheese; or Mexican-style cheese such as queso blanco, queso fresco, or panela (queso panela), unless the label clearly states that it's made from pasteurized milk. Cottage cheese, ricotta, cream cheese, processed cheese (such as American), and hard cheese (such as cheddar and Parmesan) are considered safe, as are cultured dairy products like yogurt and buttermilk.
• Unpasteurized juice. Almost all of the juice sold in the U.S. is pasteurized, but check labels to be sure. Freshly squeezed juice at smoothie bars and farmers' markets may not be pasteurized (or labeled). If you're not sure that a juice is pasteurized, skip it.
• Raw sprouts. The warm, humid conditions needed for growing sprouts are also ideal for the growth of Listeria and other bacteria. If you do eat sprouts, cook them thoroughly. Rinsing sprouts won't remove the bacteria.
• Melon that's old or not refrigerated. Refrigerate melon and eat it within a week. If cut melon sits at room temperature for more than four hours, throw it away.

Store food safely

• Check the temperature in your fridge and freezer. To help protect your food from contamination from a variety of disease-causing organisms, make sure your refrigerator is set between 35 and 40 degrees F and your freezer at or below zero. Use a refrigerator thermometer to confirm the temperature.
• Don't keep food around too long. Consume perishable and ready-to-eat food as soon as possible after you buy it, especially once you've opened it even if it hasn't yet passed the "use by" date. This date refers to unopened products. Hot dogs should be stored in the refrigerator and eaten within a week if the package is open and two weeks if unopened. Unopened packages of deli meat should be refrigerated and eaten within two weeks. Once the package is opened, eat it within 3 to 5 days.

Prepare food carefully

• Avoid contaminating food that's ready to eat. Keep any potentially contaminated food (such as unwashed produce; uncooked meat, poultry, or seafood; hot dogs; and deli meat) separate from clean produce and from cooked and ready-to-eat food. Use separate cutting boards, plates, and utensils for produce and for raw meats, poultry, seafood, and eggs.
• Wash all produce. Thoroughly wash or peel all fruits and vegetables before eating them. Don't rinse meats, poultry, or eggs.
• Cook all meat, poultry, fish, and eggs thoroughly. Use a food thermometer to test the internal temperature of meat. Most meat should be cooked to a temperature of 165 degrees Fahrenheit (or 180 degrees F in the thigh for whole poultry). If you're not measuring the temperature of the meat, cook it until it's no longer pink in the middle. Fish should be cooked until the flesh in the middle is opaque. Cook eggs until the yolk is firm. And don't sample your food before it's done.
• Reheat leftovers thoroughly. Listeria contamination can occur after food has already been cooked or processed. The bacteria can survive and, unlike many bacteria, continue to grow in the refrigerator. So heat all previously cooked leftovers to 165 degrees F or until they're steaming hot. If you use a microwave, cover the food to hold in moisture and provide safe, even heating. Allow the food to stand for a few minutes after microwaving to help complete the cooking. You can use a clean food thermometer to make sure the reheated food has reached 165 degrees F.

Keep things clean

• Wash your hands. After touching raw food, changing diapers, touching an animal, or using the bathroom, wash your hands with hot soapy water for at least 20 seconds.
• Wash surfaces and utensils. Use hot, soapy water to wash counters, cutting boards, dishes, utensils, and the sink after contact with potentially contaminated food.
• Clean dishcloths and dishtowels regularly. Used dishcloths and dishtowels can harbor bacteria. Wash them regularly in hot water. Kitchen sponges are potential sources of bacteria, too, and they're difficult to clean thoroughly. Putting them in the dishwasher or microwave only kills some of the bacteria, so if you use sponges, replace them frequently.
• Wash your refrigerator. A cold fridge is helpful but not foolproof: Listeria is a hardy organism that can survive and even continue to grow in cold temperatures (albeit more slowly). Clean your refrigerator including inside walls and shelves regularly with hot, soapy water. Use a mild liquid dishwashing detergent, rinse, then dry with a clean cloth.

Listeriosis isn't the only concern when it comes to food safety during pregnancy. Our article on foods and beverages to avoid during pregnancy will help you avoid food poisoning and other dangers.

Learn more:

• Preventing food poisoning in your home
• Is it safe to drink tap water when I'm pregnant?
• Is it safe to eat sushi while pregnant?