When a person becomes pregnant, they are often advised to avoid cold cuts and other ready-to-eat sandwich meats. This recommendation is based on a specific, potentially severe health risk: contamination with the bacterium Listeria monocytogenes. The danger lies in the infection this organism causes, known as listeriosis, which poses a unique and serious threat to both the expectant mother and the developing fetus.
Understanding the Threat of Listeriosis
Listeriosis is an infection caused by ingesting food contaminated with the bacteria Listeria monocytogenes. While rare, pregnant women are significantly more susceptible than the general healthy adult population. Hormonal changes during pregnancy cause the immune system to become less vigorous, making it harder to fight off the infection. Pregnant women are estimated to be about 10 to 20 times more likely to contract listeriosis.
For the mother, the symptoms of listeriosis are often mild, resembling a flu-like illness with fever, muscle aches, and sometimes nausea or diarrhea. However, even with mild or no symptoms, the bacteria can cross the placental barrier and infect the unborn child. This ability to move through the placenta makes the infection dangerous during gestation.
The consequences for the fetus and newborn are severe, providing the primary motivation for avoiding high-risk foods. Listeriosis can lead to devastating outcomes like miscarriage, stillbirth, or premature delivery. One report noted a fetal loss or neonatal death rate of nearly 29% in invasive cases. Babies who survive may be born severely ill with neonatal listeriosis, which can cause serious complications such as meningitis, a blood infection (sepsis), and long-term health issues. Lifelong problems, including intellectual disabilities, paralysis, seizures, or blindness, can occur in infected newborns.
Why Ready-to-Eat Meats are Vulnerable
The reason deli meats are singled out relates to the unique biology of Listeria monocytogenes and how these foods are processed and stored. Unlike many other foodborne pathogens inactivated by cold, Listeria is a psychrotolerant bacterium. This means it can survive and even multiply at refrigeration temperatures, including temperatures as low as 32°F (0°C). This characteristic defeats the traditional food safety defense of cold storage.
Ready-to-eat meats, such as sliced turkey, ham, or bologna, are processed and stored for extended periods before consumption. This gives any present Listeria time to multiply to dangerous levels. Contamination typically occurs after the meat has been cooked or pasteurized, usually during slicing, handling, or packaging at the processing plant or deli counter. The organism can survive in the food-production environment, including on surfaces and slicing machines, and can form biofilms difficult to remove through routine cleaning.
Once the vacuum-sealed package is opened or the meat is sliced at the deli, the risk of cross-contamination and growth increases, especially if stored for a prolonged time. Certain meats, such as sliced poultry products like chicken or turkey, are particularly prone to the growth of Listeria during refrigerated storage. The combination of post-processing contamination and the bacteria’s ability to thrive in the cold makes deli meats a persistent source of risk.
Safe Preparation Methods for Deli Meats
For those with strong cravings, it is possible to reduce the risk associated with deli meats by applying heat, which effectively destroys the Listeria bacteria. The recommended safety standard is to heat the meat until it reaches an internal temperature of 165°F (74°C). This temperature is sufficient to kill the pathogen, making the food safe for consumption.
The meat must be heated until it is visibly “steaming hot” throughout, as simple warming is not enough to eliminate the threat. Cold cuts can be heated in a microwave, on a stovetop, or in an oven when preparing a sandwich. Using a microwave requires extra caution because this method can heat unevenly, so ensure the entire portion is steaming hot.
It is important to consume the heated meat soon after preparation and not allow it to return to refrigeration temperatures for later consumption. Once the meat is heated to the safe temperature, the bacteria are eliminated, allowing a pregnant person to safely enjoy their sandwich.
Beyond Deli Meats: Other Listeria Risks
While deli meat is a well-known concern, listeriosis can be transmitted through other food sources that pregnant women should avoid. Any ready-to-eat food with a long refrigerated shelf life carries a potential risk. This includes unpasteurized dairy products and soft cheeses made with unpasteurized milk, such as:
- Feta
- Brie
- Camembert
- Certain Mexican-style cheeses like Queso Fresco
Other high-risk items include refrigerated pâtés and meat spreads, as well as refrigerated smoked seafood, unless the seafood is part of a cooked dish like a casserole. Raw sprouts and unwashed raw vegetables or fruits can also be sources of contamination. If a pregnant person experiences flu-like symptoms, such as fever, muscle aches, or gastrointestinal issues, and suspects consumption of a contaminated product, they should immediately contact a healthcare provider. Early diagnosis and treatment with antibiotics can prevent the infection from spreading and mitigate severe fetal complications.