Listeriosis and Pregnancy

by Marnie Webb, P.H.Ec.

Listeriosis is an infection caused by eating food contaminated with the bacterium Listeria monocytogenes. Although rare, pregnant women are twenty times more likely than other healthy adults to get listeriosis.

Healthy food choices and safe food practices protect mother and baby, contributing to a healthy pregnancy. Hormonal changes during pregnancy affect the immune system, causing pregnant women to become more susceptible to foodborne illness. While serious, foodborne risks for pregnant women can be addressed by handling food properly and by avoiding certain foods.

Foods to avoid include:

• deli meats or hot dogs unless reheated to steaming hot;
• refrigerated smoked seafood and smoked fish;
• soft and semi-soft cheese if made with unpasteurized milk;
• refrigerated pâtés and meat spreads;
• raw or undercooked meat, poultry, fish or seafood.

Listeriosis infections during pregnancy can lead to miscarriage or stillbirth, premature delivery, or infection of the newborn. Pregnant women may only experience a mild illness. Symptoms of listeriosis usually appear within 2 to 30 days but have been known to occur up to 90 days after eating contaminated food.

Listeria is prevalent in the environment. It is found in soil, water, vegetation, human and animal feces. In some processed foods like deli meats, contamination may occur after cooking but before packaging. Listeria may be present in all foods.

Listeria can survive and grow slowly at refrigeration temperatures. Listeria will grow faster at refrigerator temperatures above 4°C (40°F). You cannot tell by the look, smell or taste if
listeria is present in food. Listeria is killed by cooking food.

To reduce the risk of developing listeriosis:

• Reheat deli meats or hot dogs to steaming hot.
• Cook meat, poultry, fish and seafood to recommended temperatures; use a food thermometer.
• Follow the instructions on labels for food preparation and storage.
• Consume perishable and ready-to-eat foods as soon as possible.
• Avoid storing leftover food for more than 3 to 4 days.
• Maintain the refrigerator temperature at or below 4°C (40°F).
• Consume only pasteurized milk and milk products.
• Wash knives and cutting boards with warm soapy water after handling uncooked foods to prevent contamination of cooked and ready-to-eat foods.
• Rinse vegetables and fruit under running water before eating.

Pregnant women with questions or concerns about listeriosis are advised to consult with their health care provider.