Put food safety risks during pregnancy into perspective

Although pregnant women say they would trust information from their doctor about food safety in pregnancy, surveys of patients and clinicians alike find that the topic is often not discussed.^1,2 Consider that your pregnant patients are typically exposed to contradictory information and much freely offered advice regarding food safety. The expectant mother may be warned to not eat specific foods or to avoid entire food categories. Yet if she tries to follow all the advice, she may have very few food options left. What is she to do? Our goal in this two-part series is to address some key concerns about eating during pregnancy. Part 1 helps you guide patients on how to eat safely to avoid food-borne infection. (Part 2, which focuses on toxins, will be published in the December issue of Contemporary OB/GYN.)

By CDC estimates, 5,000 Americans die from the 76 million cases of food-borne illness in the United States each year.³ Compare this to 5,915 Americans who die on the job annually and 42,000 who die in motor vehicle accidents.⁴ Most susceptible are the very young, the very old, the immunocompromised, and those exposed to large doses of a food-borne pathogen.³ Although historically, animal products and contaminated water have been the major sources of food-borne contaminants in the United States, the importance of fresh produce as a source of food-borne illness is on the rise.⁵

Food-borne illness during pregnancy

Listeria monocytogenes

A few food-borne pathogens merit extra attention because they affect pregnant women far more than the general population. Although it's killed by pasteurization and cooking, Listeria monocytogenes (LM)-because it can be airborne-can contaminate treated foods.¹⁰ Unlike most bacteria, it's also able to grow inside a refrigerator.¹¹ Among foods most often contaminated are unpasteurized milk products and refrigerated and ready-to-eat products (dairy, meats, poultry, seafood), including deli products. Overall prevalence in high-risk food categories is 1.82% (range, 0.17–4.7%), with a higher prevalence in in-store packaged products compared to manufacturer-packaged lunch meats, deli salads, and seafood salads.¹²

RISK IS SMALL. The risk of infection is small, even if one eats a contaminated food,¹⁰ and typically causes only low-grade gastroenteritis or mild, flu-like symptoms (fever, headache, myalgia).^{13, 14} Symptoms of a more serious listeriosis infection are nausea, vomiting, abdominal pain, diarrhea with fever, and possibly meningitis, septicemia, and encephalitis. "However, the relationship between the number of L. monocytogenes [organisms] consumed (the dose) and the likelihood of illness occurring (response) in combination with the severity of the illness resulting from that dose is not well understood," according to the Cneter for Food Safety and Applied Nutrition (CFSAN).¹³

Fortunately, LM is not a common pathogen. FoodNet data for 2007 found an LM infection incidence of 0.27 cases per 100,000 population (versus 14.92 per 100,000 Salmonella infections or 12.79 per 100,000 Campylobacter infections).¹⁵ The case rate for those aged 5 to 49 years is 0.07/100,000, and newest prevalence estimates are 2,000 cases, with 420 deaths per year.^15,16

Pregnant women appear to be more likely to develop listeriosis, and one-third of all cases occur during pregnancy.¹⁰ A pregnant patient's presenting symptoms may be similar to influenza or pyelonephritis, and even if symptoms are few or very mild, LM may cross the placenta and infect the fetus.¹⁷

Deli salads are another area likely to cause confusion. On one hand, the US Department of Agriculture (USDA) includes them as worthy of caution.¹⁸ On the other hand, the FDA's most recent publications don't even list them.¹¹ According to the 2003 FDA study of risk, the most common source of infections (with >5 cases per billion servings) was 1,600 cases per year associated with deli meats.¹³

Heating sandwich meats to steaming is recommended. Canned salmon, chicken, and tuna will not cause LM contamination.