Authored by Dr. Tali Bogler and reviewed by Dr. Mark Yudin and First Exposure Medical Review Team.
Dr. Tali Bogler, MD, CCFP, MScCH, is a Medical Advisor at First Exposure, a Family physician, and Chair of Family Medicine Obstetrics at St. Michael’s Hospital, an assistant Professor, Department of Family and Community Medicine and Investigator at Li Ka Shing Knowledge Institute.
Dr. Mark Yudin, MD, MSc, FRCSC, is an Obstetrician/Gynecologist and Reproductive Infectious Diseases Specialist at St. Michael Hospital, Unity Health Toronto, and a Professor in the Department of Obstetrics and Gynecology at the University of Toronto
This health topic is an expert opinion about Listeriosis during pregnancy and lactation.
* The information provided is the expert opinion of the First Exposure Medical Advisors. It is for informational purposes only and does not replace medical care and advice from a healthcare provider. Please contact your healthcare provider if you have any concerns or to discuss any questions that you believe may be relevant to you or your baby. In case of emergency, please go to the emergency room or call 911.
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Clinical scenario:
I am pregnant and just saw on the news that the brand of lettuce I ate is being recalled because of Listeria contamination. Do I need treatment?
Q. What is Listeria/listeriosis?
A. Listeria monocytogenes are bacteria that grow on food products; Listeriosis is the infectious disease caused by consumption of foods contaminated with the bacteria. Not everyone who eats food containing Listeria will get listeriosis. Listeria can be found in soil, sewage, untreated water, as well as uncooked foods such as fish, meat, seafood, fruits, and vegetables, and dairy products (e.g., milk and cheese). See table below for some higher-risk foods and alternatives. Unlike most foodborne bacteria that do not grow at refrigerator temperatures, Listeria can grow while in the refrigerator.
Q. Who is most at risk of severe listeriosis?
A. About 130 cases of listeriosis are reported in Canada annually. People who are at highest risk of severe listeriosis include: immunocompromised individuals (people with weakened immune systems), adults over the age of 60 (risk increases with increasing age), and pregnant individuals, including their fetus or newborn. Studies show that due to physiological and immunological changes during pregnancy, being pregnant carries a 10-20 times higher risk of getting listeriosis than the general population. Listeriosis in pregnancy can lead to serious adverse maternal, pregnancy and neonatal (newborn) outcomes. Early treatment is associated with improved outcomes. Therefore prevention, early recognition, and treatment are important.
Q. What precautions can people take, especially when pregnant, to avoid listeriosis?
A. In addition to general food safety measures that should be followed, the Public Health Agency of Canada, the Society of Obstetricians and Gynaecologists of Canada, and the Canadian Food Inspection Agency all recommend avoiding foods in pregnancy known to be at increased risk of contamination with Listeria. See the following table for foods to avoid and alternatives. It is also important to be aware of Health Canada recalls (https://recalls-rappels.canada.ca/en).
Table adapted from https://www.cdc.gov/listeria/prevention/index.html
Q. What are common symptoms of listeriosis in pregnancy?
A. Many of those infected with Listeria will not have symptoms. If symptoms occur, they are similar in non-pregnant and pregnant individuals. Listeriosis can present as a flu-like illness (similar to influenza) with symptoms such as fever, fatigue, muscle aches, headache, diarrhea, and other gastro-intestinal symptoms. In severe cases, the infection can enter the blood stream (septicemia) and the tissues surrounding the brain and spinal cord, causing them to swell (meningitis). It can also lead to respiratory distress. These symptoms are non-specific and can occur within hours, days, weeks, and up to 2-3 months after consuming the contaminated food, which can sometimes make the diagnosis challenging.
Q. How is listeriosis managed in pregnancy?
A. Pregnant individuals suspecting they were exposed to Listeria and are experiencing symptoms, within 2-3 months of exposure, should contact a healthcare provider as soon as possible.
The management of someone with a possible exposure to listeria depends on whether they have symptoms of listeriosis:
No symptoms (asymptomatic)
It is generally not recommended to test or treat for listeriosis if asymptomatic. Symptoms can present 2-3 months after ingestion – if symptoms develop during this time, one should then be assessed and treated.
Symptoms but no fever
There are several approaches to management:
- close monitoring of the condition without immediate intervention (expectant management)
- obtaining blood samples to test for listeria infection in the blood stream (blood cultures). Treatment with a 14-day course of oral amoxicillin can begin right after samples are taken. Another strategy is to wait for the results of the blood culture before beginning treatment.
Fever with or without other symptoms
Blood cultures should be taken, and then intravenous ampicillin should be started. The pregnancy and the fetus should be closely monitored.
For further guidance on management of listeriosis in pregnancy, please see Listeriosis in pregnancy.
Q. Will listeriosis affect the chances of getting pregnant?
A. There is not enough information to know if listeriosis might make it harder to become pregnant in the future.
Q. Does listeriosis in pregnancy increase the chances of miscarriage?
A. Most pregnancies result in healthy babies, but there are chances of complications and unexpected outcomes in any pregnancy (without listeriosis). These chances are called baseline risks. In Canada, the baseline risk of miscarriages is approximately 15-25% (1 in 4 pregnancies). There is an increased chance of miscarriage when listeriosis occurs in the first or second trimester of pregnancy.
Q. Does listeriosis in pregnancy increase the chances of birth defects?
A. In Canada, the baseline risk of major birth defects is 3-5%. This means that 3-5 out of 100 babies born in the general population in Canada will be born with a major birth defect. Based on the available studies, it is not known if listeriosis in pregnancy increases the risk of birth defects above the baseline risk.
Q. Does Listeriosis in pregnancy increase the chances of any other harmful pregnancy outcomes?
A. Studies have shown that listeriosis in the second and third trimesters of pregnancy increases the chance of stillbirth (loss of a baby before or during delivery). The chance of stillbirth is the highest when listeriosis occurs in the second trimester. Listeriosis is also associated with higher risks of preterm birth (delivery before 37 weeks of pregnancy), low birth weight, and caesarean delivery. In addition, it can lead to infection of the uterus and the amniotic fluid (chorioamnionitis), maternal sepsis (infection in the blood), and maternal respiratory distress.
Q. Does Listeriosis in pregnancy impact the baby’s health at birth?
A. Listeriosis in pregnancy can increase the risk of neonatal (newborn) death or serious health problems in the newborn and child. Not all newborns exposed to Listeria during pregnancy will have health problems.
Listeriosis can pass to the fetus or newborn causing listeriosis in the newborn. There are two types of neonatal listeriosis:
- Early-onset listeriosis usually presents in the first 48 hours and up to 6 days of life with signs of sepsis and is thought to be transmitted through the placenta to the fetus during pregnancy.
- Late-onset listeriosis, which is less common, most often presents 7-28 days after birth, with meningitis, which if not treated quickly, can lead to long-term health problems for the child. Late-onset listeriosis is thought to be transmitted through exposure to Listeria via the birth canal during delivery.
Q. Does listeriosis in pregnancy affect future health or behavior of the child later in life?
A. Studies have not been done to see if listeriosis infection during pregnancy might affect the future health or behavior of the child later in life. As mentioned above, newborn meningitis, if not treated quickly, can lead to long-term health problems for the child.
Q. Can maternal listeriosis affect the nursing infant?
A. Studies have not been done on the safety of nursing an infant while infected with listeriosis. If you are currently nursing and have listeriosis, please speak to your healthcare provider.
Other helpful resources
Key References
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Disclaimer
First Exposure does not offer health care treatment. If you have an urgent question about your pregnancy or your baby’s health, you should contact your health care provider directly. If you don’t have a health care provider and you live in Ontario, you have a variety of health care options. In the case of an emergency, visit a hospital emergency room or call 911.