The desire for a cold-cut sandwich is a common pregnancy craving, yet the recommendation to avoid lunch meat can be confusing. This prohibition stems from a specific public health concern related to ready-to-eat products like deli meats and cold cuts. These foods, which are not reheated before consumption, can harbor bacteria that pose a unique and serious risk to a pregnant person and their developing baby. The risk is directly tied to bacterial contamination that occurs during processing and packaging.
The Primary Pathogen: Listeria Monocytogenes
The organism responsible for this food safety concern is the bacterium Listeria monocytogenes, which causes an infection known as Listeriosis. This bacterium is commonly found in the environment, inhabiting soil, water, and animal feces, and can contaminate food products during harvesting, processing, or packaging. Listeria is particularly worrisome because it is a psychrotrophic organism, meaning it can survive and even grow at typical refrigerator temperatures (40°F or lower).
Deli meats are considered high-risk because they are ready-to-eat foods that often involve multiple processing steps and handling, creating opportunities for contamination. Even if the meat is fully cooked during production, it can be contaminated afterward when it comes into contact with slicing equipment, hands, or other surfaces in a food facility or at a deli counter. This post-processing contamination, combined with the bacteria’s ability to multiply under refrigeration, is why cold cuts carry a sustained risk.
For a healthy, non-pregnant adult, a Listeria infection often results in mild, flu-like symptoms or may even be completely asymptomatic. However, the silent nature of the infection for the mother does not reflect the danger it poses to the fetus. An estimated 1,600 people contract Listeriosis each year in the United States, and while the total number is small, the consequences for vulnerable populations are severe.
Why Listeriosis Poses a Unique Threat During Pregnancy
Listeriosis is a particular concern during pregnancy because the body’s immune system undergoes natural changes that make the mother significantly more susceptible to the infection. Pregnant individuals are estimated to be about 10 to 20 times more likely to contract Listeriosis than the general population. This heightened vulnerability is due to a natural suppression of cell-mediated immunity, specifically a reduction in the function of T-cells, which are the immune cells responsible for fighting intracellular pathogens like Listeria.
The consequences for the developing fetus can be devastating, even if the mother’s symptoms are mild or non-existent. Listeria monocytogenes has a specific affinity for the placenta and possesses mechanisms, such as the bacterial protein internalin A (InlA), that allow it to breach the placental barrier. The bacteria can invade the outer layer of the placenta and pass into the fetal bloodstream.
Once the bacteria successfully cross the placental barrier, the infection can lead to several serious adverse outcomes. These outcomes include miscarriage, stillbirth, premature delivery, and severe infection in the newborn, such as neonatal sepsis or meningitis. Early treatment can improve the outcome, but about one in four pregnant people who contract the infection will lose their pregnancy or their baby shortly after birth.
How to Safely Consume Deli Meats and Cold Cuts
The risk associated with deli meats is eliminated by heat. The primary measure for safe consumption is to heat the meat to a minimum internal temperature of 165°F (74°C). This temperature is sufficient to kill the Listeria bacteria, rendering the food safe to eat.
The meat must be visibly steaming hot throughout to ensure that the entire portion has reached the target temperature. When using a microwave, check for cold spots, as uneven heating can allow pockets of bacteria to survive. The heated meat should be consumed immediately and should not be allowed to return to refrigerator temperature before eating.
Avoiding deli meats that are sliced at a deli counter can also reduce the risk of cross-contamination. These surfaces and slicers can harbor Listeria, which then transfers to the meat. Safer alternatives include shelf-stable canned meats.