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Why are pregnant women at higher risk for foodborne illness?

Listeriosis is a foodborne illness that is most likely to affect pregnant women and unborn babies. Caused by eating food contaminated with the bacterium, Listeria monocytogenes, Listeriosis can take weeks to show up. Symptoms may include fever, chills, muscle aches, diarrhea, and upset stomach. When listeriosis progresses, it can lead to stiff neck, headache, convulsions, or loss of balance. One out of five Americans who become sick with listeriosis die from the disease. Although anyone can get the illness, pregnant women appear to be more susceptible.

When a woman becomes pregnant, her body undergoes hormonal and immunological changes allowing her body to accept the fetus. Without those changes, the body's tendency would be to reject the baby and cause a miscarriage. That's because the fetus contains genetic material from the father as well as the mother, and the mother's immune system could mistake the fetus for a foreign object and try fight it off.

The adjustment in the mother's immune system involves suppressing a type of response called "cell-mediated immunity," while allowing another type of immune function (the type that involves antibodies) to remain functioning. Cell-mediated immunity is the kind involved in the rejection of organ transplants, but it is essential to control pathogens that move from cell to cell. One of those pathogens is Listeria monocytogenes.

Most food-borne pathogens attack the gastrointestinal system, but Listeria can move from the digestive tract into the bloodstream. With cell-mediated immunity restrained, Listeria infection can more easily take hold.

More than one out of four of all listeriosis diagnoses occur in pregnant women, most during the third trimester when cell-mediated immunity is at its lowest ebb. Usually, listeriosis causes only mild symptoms in the adult, but early labor and delivery is common. Miscarriage and stillbirth are serious risks.

Pregnant women can take steps to reduce their risk by avoiding foods usually associated with listeriosis. Those include:

The following web sites offer additional information about listeriosis:

Food Safety for Moms to Be: While You're Pregnant - Listeria (U.S. Food and Drug Administration)
Listeria and Pregnancy (American Pregnancy Association)
Listeria Infections (Medline Plus)
Listeriosis (CDC)
Protect Your Baby and Yourself From Listeriosis (U.S. Food Safety and Inspection Service) En Espanol

This article originally appeared in Chow Line (12/07/07), a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center, and was adapted for use on NetWellness with permission, 2007.

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Last Reviewed: Jan 07, 2010

Lydia   Medeiros, PhD Lydia Medeiros, PhD
College of Education and Human Ecology
The Ohio State University