Queso fresco, which translates to “fresh cheese,” is a soft, white, and mildly salty cheese originating from Mexico. It is a highly popular, unaged cheese known for its moist, crumbly texture that does not melt when heated, making it a common topping for many dishes. For pregnant individuals, soft cheeses like queso fresco are a concern due to the risk of bacterial contamination. The safety of consuming queso fresco during pregnancy depends entirely on the preparation method, specifically whether the milk used was pasteurized and the sanitary conditions of its production.
Understanding the Risk: Unpasteurized Dairy and Listeria
The primary pathogen responsible for making soft cheeses a concern during pregnancy is Listeria monocytogenes, the bacteria that causes the infection listeriosis. This bacterium is found widely in the environment, including soil and water, and can easily contaminate food products during processing or handling. Pregnant women are approximately ten times more likely to contract listeriosis than the general healthy population, as pregnancy alters the immune system’s response to infection.
Soft, fresh cheeses like queso fresco are particularly vulnerable environments for Listeria growth. These cheeses have a naturally high moisture content, low salt concentration, and a pH level that allows the bacteria to thrive, even under refrigeration. Unlike many other bacteria, Listeria monocytogenes can continue to multiply at typical refrigerator temperatures. While pasteurization of milk kills Listeria, the cheese can still become contaminated if the manufacturing facility is unsanitary or if the cheese is improperly handled after pasteurization.
Queso fresco does not undergo the aging process that naturally reduces moisture and increases acidity, unlike hard cheeses such as cheddar or Parmesan. Harder cheeses are generally considered safe because their lower moisture and higher salt content inhibit Listeria growth. The combination of high moisture and low acidity in queso fresco creates an ideal setting for the bacteria, which has led to multiple outbreaks linked to this type of cheese, even when made from pasteurized milk.
How to Safely Consume Queso Fresco During Pregnancy
Consuming queso fresco safely during pregnancy requires strict attention to sourcing and preparation. The most reliable safeguard is to only purchase commercially manufactured cheese that explicitly states “made with pasteurized milk” on the label. If the cheese comes from a small farm, a street vendor, or is homemade, it should be avoided due to the high risk of using unpasteurized milk or unsanitary preparation.
Even if the cheese is made with pasteurized milk, contamination can still occur during the cheese-making process. To eliminate potential risk, the cheese must be cooked until it is steaming hot. The internal temperature must reach at least 165°F (74°C) to kill any Listeria bacteria that may be present.
Since queso fresco does not melt, it is an excellent addition to baked dishes where it can be thoroughly heated. Safe consumption examples include using the cheese as a filling in enchiladas, sprinkling it on top of a hot casserole, or incorporating it into a baked dip. Simply warming the cheese is not sufficient; it must be cooked to the required internal temperature to ensure the bacteria are destroyed.
What Happens If a Pregnant Person Contracts Listeriosis
While listeriosis is relatively rare, the consequences for a pregnant person and the developing fetus can be severe. For the pregnant individual, the symptoms are often mild and flu-like, which can lead to delayed diagnosis. These symptoms may include fever, muscle aches, fatigue, and sometimes gastrointestinal issues like diarrhea or nausea.
The mild maternal illness poses serious danger to the fetus because Listeria monocytogenes can cross the placental barrier. Infection in the first trimester carries an estimated risk of miscarriage as high as 65%. Infection later in the pregnancy increases the chances of stillbirth or premature delivery.
Newborns who contract the infection may suffer from severe, life-threatening conditions such as meningitis or sepsis. Even surviving infants can face long-term health challenges, including developmental or neurological impairments. Because the maternal symptoms are often subtle, any flu-like symptoms or fever during pregnancy warrant immediate medical attention to test for and treat a possible Listeria infection with antibiotics.
Other Foods to Handle with Caution During Pregnancy
Beyond queso fresco and other soft cheeses, several other food categories carry a similar risk of Listeria or other harmful bacteria and should be consumed with caution during pregnancy.
- Deli meats, such as sliced ham, turkey, or salami, are a common source of Listeria contamination. These meats should only be eaten if they are reheated until steaming hot to 165°F.
- Refrigerated pâtés or meat spreads are considered high-risk, as their preparation and storage conditions allow Listeria to grow.
- Unpasteurized juices or ciders should be avoided, as the lack of pasteurization means harmful bacteria have not been destroyed.
- Raw sprouts, including alfalfa, clover, and radish sprouts, can harbor bacteria like Listeria or Salmonella due to the warm, moist conditions required for their growth.
- Cold-smoked seafood, unless cooked in a dish, also presents a Listeria risk and should be avoided.