Traditional Brie carries a real, if statistically small, risk of Listeria contamination during pregnancy, and most public health agencies advise against eating it. The concern is not about Brie specifically but about the category it belongs to: soft, surface-ripened cheeses whose moisture, pH, and rind environment can support the growth of Listeria monocytogenes, a bacterium that poses an outsized threat to pregnant women and their fetuses. Whether the Brie is made from pasteurized or unpasteurized milk matters, but it does not settle the question as cleanly as you might expect.
What Makes Soft-Ripened Cheese a Listeria Risk
Not all cheeses are created equal when it comes to foodborne pathogens. Hard, aged cheeses like cheddar and Parmesan have low moisture and low pH, conditions that make it difficult for most bacteria to thrive. Brie sits at the opposite end of that spectrum. Soft-ripened cheeses have higher moisture content and a pH environment that favors bacterial growth compared to other cheese types.1PubMed Central. Microbiome and Physicochemical Features Associated with Differential Listeria monocytogenes Growth in Soft, Surface-Ripened Cheeses The white, bloomy rind that gives Brie its distinctive appearance is produced by mold cultures (typically Penicillium camemberti) that raise the surface pH as the cheese ripens, creating conditions where Listeria can multiply if it gets a foothold.
Laboratory studies have confirmed that Listeria monocytogenes can grow on commercially manufactured soft cheeses even at refrigeration temperatures.2PubMed. Growth of Listeria monocytogenes in Camembert and other soft cheeses at refrigeration temperatures That is a critical detail, because many people assume their fridge keeps food safe from bacterial growth. For most pathogens that is true enough. Listeria is unusual in that it thrives in cold environments, which is part of what makes it so persistent in food processing and home kitchens alike.
Why Pasteurized Brie Is Not Automatically Safe
A common assumption is that if Brie is made from pasteurized milk, the Listeria problem disappears. Pasteurization is extraordinarily effective at killing the bacterium. Standard high-temperature, short-time pasteurization at 72°C for 15 seconds can achieve at least an 11-log reduction of L. monocytogenes in milk, which essentially means it wipes the organism out entirely.3PubMed. Predictive modelling of inactivation of Listeria spp. in bovine milk during high-temperature short-time pasteurization So the milk that goes into a pasteurized Brie starts clean.
The problem is what happens afterward. Because Listeria is inactivated by pasteurization, the majority of illness cases linked to cheese have been traced to environmental and cross-contamination of fresh-soft, soft-ripened, and semi-soft cheeses after the milk was pasteurized.4PubMed Central. Listeria monocytogenes cross-contamination of cheese: risk throughout the food supply chain The bacterium can enter the cheese during curd handling, brining, aging, packaging, or at any other point in the supply chain where the cheese is exposed to the environment. Once on the cheese surface, the soft, moist, pH-friendly conditions let it multiply.
Real-world outbreaks illustrate this vividly. Two separate listeriosis outbreaks in British Columbia, Canada, were caused by soft ripened cheese even though pasteurized milk was used and the pasteurization process itself was ruled out as the contamination source. In one case, the likely route was from farm animals to personnel to culture solutions used during cheese production. In the other, birds contaminated the dairy plant’s water supply during the curd-washing step.5PubMed Central. Listeriosis outbreaks in British Columbia, Canada, caused by soft ripened cheese contaminated from environmental sources These are not stories about raw milk. They are stories about how easily Listeria infiltrates a cheese-making environment.
Even aging does not reliably eliminate the risk. Research has shown that cheese held for 60 days, the minimum aging period required by U.S. regulations for raw-milk cheese, still supported growth from very low initial levels of Listeria monocytogenes introduced after processing, regardless of whether the cheese was made from raw or pasteurized milk.6Journal of Food Protection. 60-Day Aging Requirement Does Not Ensure Safety of Surface-Mold-Ripened Soft Cheeses Manufactured from Raw or Pasteurized Milk When Listeria monocytogenes Is Introduced as a Postprocessing Contaminant The cheese itself is the hospitable environment, and the 60-day rule that protects consumers from many other pathogens does not reliably work against this one.
Why Pregnant Women Face a Disproportionate Risk
Listeriosis is rare in the general population, but pregnancy changes the math dramatically. The immune shifts that allow your body to tolerate a genetically distinct fetus also reduce your ability to fight off certain intracellular pathogens. Pregnant women are at a much higher risk of listeriosis compared to the general population, and the consequences can include miscarriage, stillbirth, and preterm labor.7PubMed Central. Listeria in Pregnancy-The Forgotten Culprit Estimates from public health agencies typically put pregnant women’s risk at roughly 10 to 20 times higher than the general adult population.
Part of what makes L. monocytogenes so dangerous in pregnancy is its affinity for placental tissue. The bacterium uses a surface protein called internalin A to latch onto a receptor called E-cadherin, which is present on the cells lining the placental barrier. Research has shown that bacterial entry into these cells occurs through the same molecular interaction that the bacterium uses to cross the intestinal barrier, and that this mechanism is exploited to target and cross the placental barrier as well.8PubMed Central. Targeting and crossing of the human maternofetal barrier by Listeria monocytogenes: role of internalin interaction with trophoblast E-cadherin In other words, Listeria has a molecular toolkit that lets it break into the one place where infection does the most harm during pregnancy.
Experimental work on placental tissue has confirmed that without the internalin A protein, the bacterium is nearly unable to invade placental explants, which underscores how central this one mechanism is to fetal infection.9PLoS Pathogens. Placental Syncytiotrophoblast Constitutes a Major Barrier to Vertical Transmission of Listeria monocytogenes The placenta does mount a defense: its outer layer acts as a significant barrier. But when enough bacteria make it through, the fetus has almost no immune defenses of its own.
Symptoms, Timing, and Why It Is Easy to Miss
One of the more frustrating aspects of listeriosis in pregnancy is that the symptoms in the mother are often mild and nonspecific. When a pregnant woman shows symptoms at all, the illness typically resembles the flu: fever, headache, diarrhea, and muscle aches.10PubMed Central. An Update Review on Listeria Infection in Pregnancy Many women might chalk this up to a routine bug and never seek testing. The fetal consequences, however, can be severe: premature birth, sepsis, central nervous system involvement, or death.
The timeline makes detection even harder. For pregnancy-associated listeriosis, the median incubation period is about 27.5 days, with a range from 17 to 67 days.11PubMed Central. What is the incubation period for listeriosis? That is nearly a month between eating the contaminated food and developing symptoms. By the time you feel unwell, you may have no memory of the specific meal that caused the problem. This long lag also differs from the impression most people have of food poisoning, where symptoms appear within hours. With Listeria, weeks can pass. For context, gastrointestinal listeriosis in non-pregnant adults has a median incubation of about 24 hours, so the pregnancy-associated form operates on a completely different timescale.11PubMed Central. What is the incubation period for listeriosis?
What Happens If You Are Diagnosed
If listeriosis is caught, treatment with antibiotics can be effective. A review of case reports found that among 13 women who developed listeriosis in the first or second trimester of pregnancy, all eight cases in which both mother and baby survived without lasting harm were treated with ampicillin or penicillin, sometimes combined with gentamicin. Intravenous ampicillin, with or without gentamicin, effectively sterilizes the placenta and can prevent maternal and fetal illness and death in early pregnancy.12Emerging Infectious Diseases. Treatment of Listeriosis in First Trimester of Pregnancy The challenge, again, is getting diagnosed in time. Because the symptoms mimic a mild viral illness, blood cultures are not always ordered early enough.
If you are pregnant and develop an unexplained fever, especially if you recall eating a high-risk food in recent weeks, it is worth mentioning this to your healthcare provider so they can consider testing for Listeria. The infection is treatable, but treatment works best when started early.
The Confusing Patchwork of Official Guidelines
If you have tried to figure out which cheeses are safe by reading official guidance, you have probably noticed that the advice is not entirely consistent. Public health agencies broadly agree on one principle: only eat soft cheese during pregnancy if it is made from pasteurized milk. But the details get muddled. Some agencies recommend avoiding all raw-milk cheeses and all products made from unpasteurized milk. Others focus specifically on soft and semi-soft varieties. And as one analysis of guidelines noted, contradictory statements sometimes appear within the same publication from the same agency.13Graduate Journal of Food Studies. Cheesemongers Over Fearmongers: Toward Data Driven Cheese Recommendations for Pregnant Women
The confusion partly reflects a real scientific gray area. The risk from a pasteurized Brie is genuinely lower than from a raw-milk Brie, but it is not zero because of the post-pasteurization contamination problem described above. Meanwhile, a hard aged cheese made from raw milk (like a well-aged Gruyère) is probably lower risk than either, because its low moisture and low pH create a hostile environment for Listeria. But saying “some raw-milk cheeses are safer than some pasteurized soft cheeses” is a complicated public health message, and most agencies opt for simpler blanket rules.
Regulatory approaches to Listeria in ready-to-eat foods also vary by country. Some jurisdictions adopt a zero-tolerance model (no detectable Listeria in 25 grams of product), while others allow up to 100 colony-forming units per gram, depending on whether the product supports further growth.14PubMed Central. Listeria monocytogenes in Ready-to-Eat Foods: Risk Perspectives Across Different Regulatory Systems What counts as “safe enough” at the regulatory level varies depending on where you live, which adds another layer of confusion for anyone trying to parse the rules.
Practical Ways to Reduce Risk If You Want to Eat Brie
The most conservative approach is simply to avoid soft-ripened cheeses like Brie and Camembert for the duration of your pregnancy. That is what most guidelines recommend, and it eliminates the risk entirely. But if you want to be more nuanced, a few practical considerations can help.
Cooking soft cheese to a temperature that steaming-hot throughout (above about 75°C or 165°F) kills Listeria effectively. Baked Brie, melted into a hot dish, or used in a thoroughly cooked recipe is far safer than Brie eaten cold from the cheese board. The bacterium is heat-sensitive; the issue has always been that these cheeses are typically consumed without further cooking.
Beyond cooking, consider the supply chain. Brie bought pre-packaged from a large commercial producer with rigorous food safety testing is a different proposition from a wedge cut at a farmers’ market stall or a specialty cheese counter where knives, boards, and surfaces may harbor environmental contamination. Cross-contamination of foods with L. monocytogenes is a continuous risk throughout the food supply chain.4PubMed Central. Listeria monocytogenes cross-contamination of cheese: risk throughout the food supply chain Every additional surface the cheese touches between the factory seal and your plate is a chance for contamination.
- Safest option: Skip soft-ripened cheeses entirely during pregnancy.
- Lower-risk compromise: Eat Brie only when cooked to steaming-hot temperatures throughout.
- If eating uncooked: Choose factory-sealed, pasteurized Brie from a reputable commercial producer. Avoid deli-counter cuts, buffet cheese boards, and cheeses past their use-by date.
None of these steps eliminate risk to absolute zero, but they shift it substantially. The last option on the list still carries some residual risk from post-pasteurization contamination, which is why most agencies do not endorse it for pregnant women.
Hard Cheese, Cream Cheese, and Other Safer Alternatives
You do not have to give up cheese entirely. The moisture and pH conditions that make soft-ripened cheese hospitable to Listeria are largely absent in hard and semi-hard cheeses. Research on growth conditions for L. monocytogenes in cheese matrices has shown that low water activity significantly limits the bacterium’s ability to initiate growth, even when contamination levels are low.15ScienceDirect (Journal of Food Protection). Effect of pH and Water Activity on the Growth Limits of Listeria monocytogenes in a Cheese Matrix at Two Contamination Levels Hard, aged varieties like cheddar, Parmesan, and Manchego have low water activity and are generally considered safe even when made from raw milk, because the aging process and drier texture make bacterial growth unlikely.
Processed cheeses, cream cheese, and cottage cheese are also lower risk because they are typically made from pasteurized milk and consumed soon after production in sealed containers, limiting the window for environmental contamination. The cheeses to watch out for are specifically the soft-ripened and surface-ripened types: Brie, Camembert, certain blue cheeses, and fresh soft cheeses like queso fresco that have been linked to outbreaks.
What About Plant-Based Cheese Alternatives
With the rise of vegan and dairy-free cheese, some pregnant women wonder whether plant-based alternatives dodge the Listeria issue entirely. They do avoid the traditional soft-cheese risk factors, but they are not universally free of concern. A recent study evaluating 37 plant-based cheese products found that while Listeria and Salmonella were not detected in initial samples, growth of L. monocytogenes was observed at 8°C in one Parmesan-type analogue whose pH, water activity, and moisture favored persistence.16PubMed Central. Microbiological quality of plant-based cheese analogues and pathogen behavior in cashew nut-based varieties in cashew nut-based varieties Most plant-based analogues did not support significant pathogen growth, but the finding is a reminder that the bacterium does not care whether a food is dairy or not. If the moisture, pH, and nutrient conditions are right, Listeria can grow.
Plant-based cheeses also tend to be less rigorously regulated and tested for Listeria compared to dairy products, which have decades of food safety infrastructure built around them. If you are switching to plant-based alternatives specifically for food safety during pregnancy, they are likely lower risk overall, but they are not a guaranteed safe harbor. The same basic hygiene principles apply: keep them refrigerated, eat them before their use-by date, and be cautious with products that feel moist and soft rather than firm and dry.
Other Foods That Carry the Same Risk
It is worth noting that Brie gets an outsized share of the public’s attention on this topic, partly because it is the most recognizable soft-ripened cheese and partly because pregnancy food lists tend to single it out by name. But the underlying risk factors, high moisture and a pH that permits Listeria growth, apply to many other foods. Deli meats, smoked fish, pre-prepared salads, and even cantaloupe have caused listeriosis outbreaks. If you are pregnant and trying to reduce risk, focusing exclusively on Brie while eating cold cuts straight from the deli counter misses the bigger picture. The same principles apply across the board: heat kills Listeria, refrigeration slows but does not stop it, and the more a ready-to-eat food has been handled and exposed to the environment between production and your plate, the higher the chance of contamination.