What Causes Listeria & Foods to Avoid in Pregnancy

Quick answer: Listeria comes from food — almost always a ready-to-eat product contaminated at the factory, the deli, or somewhere in the supply chain. The foods most often linked to outbreaks are deli meats, soft cheeses (especially queso fresco-style), refrigerated smoked seafood, raw milk and raw-milk products, cantaloupes and other pre-cut fruit, packaged salads, ice cream, and pâté. Pregnant women should avoid these or reheat them to steaming hot.

How food becomes contaminated

Listeria monocytogenes lives in soil and water and in the intestines of farm animals. It’s everywhere in agriculture — that part is not unusual. What makes it dangerous in food is that listeria can survive and even grow at refrigerator temperatures (below 40 °F), and it can establish itself in the wet, cold corners of a food-processing facility — drains, slicer blades, conveyor seams, floor cracks — and persist there for months or years. The FDA notes that heat above 165 °F kills it, but most of these foods are eaten without a final “kill step” between the factory and your plate.

That’s why, when an outbreak happens, the contaminated product is almost always something that was meant to be eaten right out of the package: a sealed Boar’s Head liverwurst, a cup of Big Olaf ice cream, a package of Jensen Farms cantaloupe, a refrigerated caramel apple. The contamination happened at the producer, and the consumer had no way to detect it — listeria has no smell, no taste, and no visible mold.

Foods to avoid during pregnancy

This is the FDA and ACOG short list. It is not exhaustive — listeria can show up in unexpected products — but these are the categories with repeat outbreak histories.

Avoid or reheat to steaming hot (165 °F)

• Deli meats and lunch meats — ham, turkey, roast beef, salami, mortadella. The 2024 Boar’s Head outbreak killed at least 10 people; one Minnesota mother nearly lost her unborn child. Reheat to steaming hot or skip.
• Hot dogs — same category. Cook until steaming before eating.
• Refrigerated pâté and meat spreads.
• Refrigerated smoked seafood — lox, nova-style salmon, kippered fish, smoked trout. Canned or shelf-stable versions are fine. Hot-smoked seafood in a cooked dish (like a casserole) is fine.

Avoid entirely

• Soft cheeses made from unpasteurized milk — including queso fresco, panela, queso blanco, requesón, brie, camembert, feta, and blue-veined cheeses unless the label clearly says “made with pasteurized milk.” This is the largest single risk for Hispanic pregnant women, who get listeriosis at about 24 times the rate of non-Hispanic women.
• Raw (unpasteurized) milk and anything made with it.
• Unpasteurized juice and unpasteurized cider.
• Raw sprouts — alfalfa, clover, radish, mung bean. Cook before eating.
• Raw or undercooked seafood, eggs, meat, and poultry.

Foods to be careful with

• Pre-cut and packaged fruit, especially cantaloupe — keep refrigerated and eat within a day or two. The 2011 Jensen Farms outbreak (cantaloupe) killed 33.
• Pre-packaged salads and salad bar items — these have caused outbreaks too.
• Ice cream — the 2014 Big Olaf and other ice cream outbreaks affected pregnant women. Avoid soft-serve from machines that aren’t routinely sanitized.
• Caramel apples — the stick inserted into the apple creates an entry point for listeria. There was a fatal outbreak in 2014.
• Eggnog, mousse, tiramisu, hollandaise, Caesar dressing — anything made with raw eggs.

Why “made with pasteurized milk” still isn’t a guarantee

Even soft cheeses made with pasteurized milk have caused listeria outbreaks when the facility itself was contaminated. The pasteurization happens upstream of the cheese being formed and packaged; if listeria lives on equipment or in drains, it can re-contaminate the finished product. The FDA recommends that pregnant women avoid queso fresco-style cheeses entirely regardless of label, because of repeated outbreaks.

Why recalls happen weeks or months after the food was eaten

Public health departments only spot a listeria outbreak when they have at least two patients whose bacterial DNA fingerprint (sequenced via PulseNet) matches. With about 1,600 cases a year spread across the country and a 2–10 week incubation period, that match often takes a while. By the time the recall is announced, you may have already eaten the product and may already be infected.

If a recall is announced and you ate the product within the past 10 weeks, call your doctor — even if you feel fine. ACOG’s guidance walks them through the right questions and tests.

If contaminated food caused your infection

U.S. law treats listeria contamination in ready-to-eat food as a violation, with zero tolerance: any detectable amount is grounds for a recall. When that contamination causes a pregnancy loss, neonatal infection, or any other harm, the producer can be held legally responsible. The food safety attorneys at Pritzker Hageman have brought many of these cases — see their page on listeriosis and miscarriage and their page on babies born with listeriosis for more on legal options.

Sources: FDA — Food Safety for Moms-to-Be · ACOG — Listeria and Pregnancy · CDC — People at Increased Risk for Listeria Infection · FDA — Get the Facts about Listeria.