Listeria Infection in Pregnancy

Expecting women know that eating a healthy diet is important for fetal development. You may know what foods are best for you and your unborn baby, and you likely know to abstain from alcohol, drugs, and certain medications during pregnancy—but do you know about food safety and contamination from listeria?

The bacteria listeria monocytogenes can cause the infection listeriosis. The Centers for Disease Control and Prevention (CDC) estimates that 2,500 people become seriously ill with listeriosis each year in the United States. In pregnancy, this maternal infection can also infect the baby and, if contracted early, cause miscarriage. An infection occurring later in pregnancy can cause Intrauterine Growth Restriction (IUGR), and in the third trimester, listeria can be a cause for premature labor, premature delivery, and ultimately can cause neonatal sepsis, meningitis, and death. The meningitis in the baby can even develop after the first few weeks of life.

What Is Listeriosis?

Listeria bacteria are commonly found in soil and groundwater. Up to one in twenty adults have this bacterium in their feces, so the listeriosis infection is a fecal-oral route, much like the feline-caused toxoplasmosis. Additionally, foods such as soft cheeses and raw meat can be contaminated with listeria—the cause of most infections in people.

In private practice, listeriosis is an easily missed infection. Fairly weakly infectious bacteria, listeria usually target the immuno-compromised, such as persons with AIDS, diabetes, or pregnancy. In fact, according to CDC data, pregnant women are about 20 times more likely than other healthy adults to get listeriosis—and one-third of listeriosis cases happen during pregnancy.

The true frequency of infection affecting pregnancy is unknown for several reasons. First of all, few obstetricians get routine cultures on miscarriages, assuming correctly that miscarriage is usually the result of genetic mishaps, especially in the absence of maternal symptoms. Because listeria is not checked for scrupulously, and because it seems to be everywhere in contaminated products, the epidemiology statistics are still quite a mess.