As part of National Nutrition Month, we'd be remiss to overlook concerns in pregnancy over foods to avoid and why. Many foods on the "no-no"/caution list in pregnancy are on that list due to the food-borne illness called listeriosis, caused by bacteria called Listeria. Listeria is a type of bacteria that infects mammals through contaminated food. It is found in soil, water, and some animals. Unlike some other bacteria, Listeria can live in cold environments, like the refrigerator. Listeria is killed by cooking and pasteurization.
Known foods that can harbor Listeria bacteria include:
- improperly pasteurized milk
- unpasteurized dairy (raw milk, for example)
- cheeses (soft unripened like cottage cheese, cream cheese, and ricotta; soft cheese like queso fresco, queso de crema, and queso de puna, feta, brie, camembert)
- ice cream, butter, cream
- raw vegetables
- raw sprouts
- fermented raw-meat sausages
- raw and cooked poultry
- deli meats
- smoked seafood
- hotdogs not reheated
- pate and meat spreads
- cooked, ready-to-eat crustaceans
Now before you go throwing out nearly everything in your fridge, let's look a little closer at the more common foods that cause listeriosis. Just because a food is on the list doesn't mean the risk is equal -- some foods have a higher percentage for causing illness than others. For example, there are 1,591 more yearly cases of listeriosis from deli meat (when eaten cold/not heated) than from soft unripened cheeses. And here's another interesting fact -- average, ordinary pasteurize milk is considered a moderate risk for Listeria. All this talk of soft unripened cheese and who knew that milk was on the list too! The risk factor goes up for milk not because it's more likely to harbor Listeria, but because we tend to consume it more frequently than soft unripened cheese and therefore are at a greater risk.
According the the United States Food and Drug Administration (FDA), the following foods are broken down into risk categories as follows (full report source):
- Deli meats (not heated)
- Hotdogs (not reheated)
- Pate and meat spreads
- Raw/unpasteurized milk
- Smoked seafood
- Cooked, ready-to-eat crustaceans
- High fat/other dairy products
- Soft unripened cheese
- Pasteurized liquid milk
- Fresh, soft cheese
- Hotdogs reheated
- Preserved fish
- Raw seafood
- Dry/semi-dry fermented sausages
- Semi-soft cheese
- Soft ripened cheese
- Deli type salads
- Ice cream and other frozen dairy products
- Processed cheese
- Cultured milk products
- Hard cheese
Why Is Listeriosis a Problem for Pregnancy?
The fact is that anyone -- pregnant or not -- can develop listeriosis. However, pregnancy supresses the immune system, which can make fighting it off more difficult. According to the American College of Obstetricians and Gynecologists (ACOG), listeriosis occurs in pregnant people 13 times more than in non-pregnant persons (the Centers for Disease Control says pregnant women are 20 times more likely to develop listeriosis). However, keeping things in perspective, only 17% of the annual reported cases of listeriosis are from pregnant people (American Pregnancy Association). Developing listeriosis is linked with an increased risk of miscarriage, premature birth, newborn infection, and stillbirth or newborn death (approximately 22%).
What to Look For
There can be a long incubation period for listeriosis, which means that it can be up to 30 days after you've been exposed before you show symptoms. Symptoms of listeriosis are similar to that of the flu -- muscle aches, headache, fever, nausea, vomiting. Your care provider can confirm or rule out listeriosis by a simple blood test.
The Good News
If you think you have been exposed to Listeria or have developed listeriosis, there is treatment available. Early treatment with antibiotics may prevent infection and resulting complications. It's important to notify your doctor or midwife to let them know if you have or think you have been exposed to Listeria. They will be able to help you with the best course of treatment. Dr. Jeffrey L. Ecker, chair of the ACOG’s Committee on Obstetric Practice and writer of the Committee Opinion paper on Listeria, helped allay fears by saying, "Fortunately most women who are exposed won’t develop a listeria infection, and in many cases, careful observation for fever or other signs and symptoms is all that is needed."
Of course, the best treatment is prevention. Now that you know a little more of the level of risk for different kinds of foods, you can create an informed opinion and stance on what to watch for. And know that in some cases, absolute avoidance is not necessary -- eat deli meat and hotdogs that are heated thoroughly!