416-813-6780 (Toronto and GTA)
Alcohol and Substance
Pregnancy & Breastfeeding Resources
Read more in our News Archive
Food-borne illnesses during pregnancy : Prevention and treatment
Carolyn Tam, Aida Erebara, MD and Adrienne Einarson, RN
After hearing about outbreaks of illness resulting from Listeria and Salmonella, many of my patients are wondering about the risks of food-borne illnesses during pregnancy and what they can do to reduce their chances of contracting them.
Although heating or cooking food is the best way to inactivate food-borne pathogens, improved standards and surveillance have reduced the prevalence of contaminated foods at grocery stores.Therefore, it is no longer necessary for pregnant women to avoid foods like deli meats and soft cheeses (associated with Listeria); soft-cooked eggs (associated with Salmonella); or sushi and sashimi. Regardless of whether seafood is raw or cooked, pregnant women should choose low mercury seafood (eg, salmon and shrimp) over higher mercury varieties (eg, fresh tuna). Pregnant women should ensure that their food is obtained from reputable establishments; stored, handled, and cooked properly; and consumed within a couple of days of purchasing.
Après avoir entendu parler déclosions de maladies causées par les Listeria et les Salmonella, plusieurs de mes patientes se posent des questions sur les risques des maladies transmises par les aliments durant la grossesseet sur les façons de réduire les possibilités de les contracter.
Cest en chauffant ou en cuisant les aliments quon peut le mieux inactiver les pathogènes quils contiennent, mais de meilleures normes et une plus grande surveillance ont aussi réduit la prévalence daliments contaminés dans les épiceries. Par conséquent, il nest plus nécessaire pour les femmes enceintes déviter des aliments comme les charcuteries etles fromages à pâte molle (associés avec les Listeria), les œufs à la coque (associés aux Salmonella) ou encore les sushis et les sashimis. Quimporte si les fruits de mer sont crus ou cuits, les femmes enceintes devraient choisir des produits à faible teneur en mercure (p. ex. saumon et crevettes) plutôt que les variétés à plus forte concentration en mercure (p. ex. thon frais). Les femmes enceintes doivent assurer que leurs aliments proviennent détablissements dignes de confiance, quils sont entreposés, manipulés et cuits correctement,et consommés dans les quelques jours qui suivent leurachat.
In general, populations at increased risk of illness relating to infected food are characterized by compromised immune function.1 Hormonal changes that occur during pregnancy decrease cell-mediated immune function, thus increasing the susceptibility of pregnant women to certain types of infections.2 Food-borne pathogens of special concern for pregnant women include Listeria monocytogenes and Salmonella enterica, as maternal infection might increase the risk of adverse pregnancy outcomes.
Soft-ripened cheeses, deli meats, refrigerated ready-to-eat foods
Unpasteurized milk, soft-ripened cheeses, and refrigerated ready-to-eat meats and seafood have been implicated in past outbreaks of listeriosis,3 an infection caused by the Gram-positive bacterium L monocytogenes. Although increased surveillance of potential sources of contamination has reduced the frequency of outbreaks of listeriosis,4 the incidence among pregnant women remains about 20 times higher compared with the general population.5
Maternal infection might be asymptomatic or it might present with mild flulike symptoms, including fever, muscle aches, and gastrointestinal symptoms, such as nausea or diarrhea.6 In contrast to maternal illness, fetal or neonatal infection is often severe and potentially fatal. Sequelae of intrauterine infection include spontaneous abortion, stillbirth, preterm labour, and early-onset neonatal sepsis.68 Appropriate management of maternal listeriosis with a broad-spectrum antibiotic (eg, ampicillin or penicillin) can reduce the risk of adverse fetal outcomes.
Anecdotal reports suggesting an association between recurrent miscarriage and chronic or asymptomatic listeriosis remain unsubstantiated.8 In a prospective study of 86 women with 2 or more previous miscarriages, L monocytogenes was not isolated from the reproductive tract of any of the women.9
If food is properly handled and stored, the risk of being infected with L monocytogenes appears to be low. Therefore, pregnant women need not avoid soft-ripened cheeses or deli meats, so long as they are consumed in moderation and obtained from reputable stores. Hard cheeses, cream cheese, cottage cheese, and shelf-stable items are not associated with L monocytogenes and are generally safe to consume.10
Raw or soft-cooked eggs
Eggs are among the most common causes of Salmonella infection, a food-borne illness caused by nontyphoid Salmonella bacteria.11 The collaborative effort of numerous regulatory agencies has helped increase the safety of eggs.12,13 In the United States, estimates of the frequency of infected eggs range from approximately 1 in 30 000 to 1 in 10 000.14,15
Like other food-borne illnesses, Salmonella infection (for which pregnant women are not at increased risk) typically presents with fever and gastrointestinal symptoms, such as nausea, vomiting, stomach cramps, and diarrhea16; however, bacteremia, which is estimated to occur in approximately 4% of cases, might lead to intrauterine sepsis.17 Therefore, pregnant women should avoid raw or undercooked eggs, unless pasteurized eggs have been used in place of shell eggs. Homemade foods that often contain raw eggs include mayonnaise and salad dressings; custards and ice creams; and raw cookie dough and cake batter. Commercial products are made using pasteurized eggs; therefore, these items are safer to consume.
Raw fish and shellfish
Seafood-related food-borne illness is most commonly associated with the consumption of raw or under-cooked seafood. In general, shellfish account for more seafood-related infections than finfish, as the latter are usually consumed fully cooked.18 Pathogens associated with the consumption of seafood include noroviruses, Vibrionaceae and Salmonella (bacteria) species, and some helminthic and protozoan species.18,19
Infection by seafood-related pathogens has not been well studied in pregnancy, and for the most part infection is limited to the gastrointestinal tract and is usually self-limiting.18 Treatment s aimed at maintaining adequate fluid and electrolyte balance,18 with severe or invasive bacterial infection requiring treatment with antibiotics.18 Penicillins, cephalosporins, and fluoroquinolones are commonly used and are not associated with an increased risk of birth defects or any other adverse pregnancy outcomes.2024 Most parasites found in seafood do not cause illness in humans19; however, when infection does occur, nutritional deficiencies might result.
Seafood marketed for human consumption undergoes screening for microbial contamination,19 thus increasing the safety of commercially available products. Cooking is the most effective method for inactivation of parasites, although flash-freezing is also effective and is often used for sushi-grade fish. Pregnant women need not avoid raw fish if it is obtained from a reputable establishment, stored properly, and consumed soon after purchase. Women should imit their consumption of high mercury fish and shellfish, including fresh tuna and yellowtail,25 although low mercury alternatives (eg, salmon, crab, and shrimp) can be consumed more regularly.25
Botulism is a paralytic disease caused by neurotoxins produced by the Clostridium botulinum bacterium. The consumption of honey, which might be contaminated with clostridia spores, has been identified as a risk factor for infant botulism,26 a form of botulism that occurs when bacterial spores germinate and colonize the lumen of the large intestine of the neonate.27 Compared with that of the neonate, the adult gut is less conducive to the growth of the clostridia bacteria owing to increased colonization with protective microflora.28 Therefore, colonization botulism, which describes the analogous disease in adults, is extremely rare and occurs almost exclusively among individuals with underlying gastrointestinal abnormality or recent antibiotic treatment.29,30
The molecular weight of the botulinum toxin is approximately 150 kDa; therefore, it is unlikely to cross the placenta via passive diffusion.31 A case report in which a woman acquired botulism during pregnancy suggested that there is no increased risk to the fetus.28 Together with the low risk of colonization botulism among healthy adults, women without gastrointestinal pathology do not need to avoid honey during pregnancy.
Food safety is a concern for all individuals but even more so for the pregnant woman and the fetus, as they might be more susceptible to some food-borne illnesses with serious sequelae. Food-borne pathogens of concern for pregnant women include L monocytogenes and S enterica; these organisms can be passed to the fetus and increase the risk for spontaneous abortion, stillbirth, or perinatal complications. If properly handled and prepared, the chance of a food being infected with L monocytogenes is low. Therefore, pregnant women can consume soft cheeses, deli meats, and refrigerated ready-to-eat foods in moderation, so long as they are obtained from reputable establishments and consumed soon after purchase. Similarly, raw fish (eg, sushi and sashimi) can be consumed in moderation, although women should still choose low mercury fish, such as salmon and shrimp, over higher mercury varieties, such as fresh tuna. Although consumption of raw shell eggs is among the most common cause of Salmonella infection in humans, the overall risk appears to be low; however, safer alternatives (eg, pasteurized eggs) are widely available and can be used as substitutes in most recipes requiring raw eggs. As general guidelines to food safety, pregnant women should ensure that their food is obtained from reputable establishments;< stored, handled, and cooked properly; and consumed in a timely manner.
Can Fam Physician
Vol. 56, No. 4, April 2010, pp.341 - 343
Copyright © 2010 by The College of Family Physicians of Canada
- Smith JL. Long-term consequences of foodborne toxoplasmosis: effects on the unborn, the immunocompromised, the elderly, and the immunocompetent. J Food Prot 1997;60(12):1595611. [Google Scholar]
- Smith JL. Foodborne infections during pregnancy. J Food Prot 1999;62(7):81829. [Medline]
- US Department of Health and Human Service, US Food and Drug Administration. Quantitative assessment of relative risk to public health from foodborne Listeria monocytogenes among selected categories of ready-to-eat foods. Silver Spring, MD: US Food and Drug Administration; 2003. Available from: www.fda.gov/Food/ScienceResearch/ResearchAreas/RiskAssessmentSafetyAssessment/ucm183966.htm. Accessed 2010 Feb 24
- Silver HM. Listeriosis during pregnancy. Obstet Gynecol Surv 1998;53(12):73740. [Medline]
- Southwick FS, Purich DL. Intracellular pathogenesis of listeriosis. N Engl J Med 1996;334(12):7706. Full text
- Janakiraman V. Listeriosis in pregnancy: diagnosis, treatment, and prevention. Rev Obstet Gynecol 2008;1(4):17985. [Medline]
- Gellin BG, Broome CV. Listeriosis. JAMA 1989;261(9):131320. Link to full text
- Mylonakis E, Paliou M, Hohmann EL, Calderwood SB, Wing EJ. Listeriosis during pregnancy: a case series and review of 222 cases. Medicine (Baltimore) 2002;81(4):2609. [Medline
- Manganiello PD, Yearke RR. A 10-year prospective study of women with a history of recurrent fetal losses fails to identify Listeria monocytogenes in the genital tract. Fertil Steril 1991;56(4):7812. [Medline]
- Centers for Disease Control and Prevention. Listeriosis. Atlanta, GA: Centers for Disease Control and Prevention; 2008. Available from: www.cdc.gov/nczved/dfbmd/disease_listing/listeriosis_gi.html. Accessed 2010 Feb 24.
- Lynch M, Painter J, Woodruff R, Braden C. Surveillance for foodborne-disease outbreaksUnited States, 19982002. MMWR Surveill Summ 2006;55(10):142. [Medline]
- Mumma GA, Griffin PM, Meltzer MI, Braden CR, Tauxe RV. Egg quality assurance programs and egg-associated Salmonella enteritidis infections, United States. Emerg Infect Dis 2004;10(10):17829. [Medline]
- Braden CR. Salmonella enterica serotype enteritidis and eggs: a national epidemic in the United States. Clin Infect Dis 2006;43(4):5127. Epub 2006 Jul 3. [Abstract/Full Free Text]
- Ebel E, Schlosser W. Estimating the annual fraction of eggs contaminated with Salmonella enteritidis in the United States. Int J Food Microbiol 2000;61(1):5162. [Medline]
- Schroeder CM, Latimer HK, Schlosser WD, Golden NJ, Marks HM, Coleman ME, et al. Overview and summary of the Food Safety and Inspection Service risk assessment for Salmonella enteritidis in shell eggs, October 2005. Foodborne Pathog Dis 2006;3(4):40312. [Medline]
- Kendall P, Medeiros LC, Hillers V, Chen G, DiMascola S. Food handling behaviors of special importance for pregnant women, infants and young children, the elderly, and immune-compromised people. J Am Diet Assoc 2003;103(12):16469. [Medline]
- Scialli AR, Rarick TL. Salmonella sepsis and second-trimester pregnancy loss. Obstet Gynecol 1992;79(5 Pt 2):8201. [Medline]
- Butt AA, Aldridge KE, Sanders CV. Infections related to the ingestion of seafood. Part I: viral and bacterial infections. Lancet Infect Dis 2004;4(4):20112. [Medline]
- Butt AA, Aldridge KE, Sanders CV. Infections related to the ingestion of seafood. Part II: parasitic infections and food safety. Lancet Infect Dis 2004;4(5):294300. [Medline]
- Heinonen OP, Slone D, Shapiro S. Birth defects and drugs in pregnancy. Littleton, MA: Publishing Sciences Group; 1977. p. 297, 435313. [Google Scholar]
- Briggs GG, Freeman RK, Yaffe SJ. Drugs in pregnancy and lactation. 8th ed ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2008. p. 86, 273295. [Google Scholar]
- Czeizel AE, Rockenbauer M, Sψrensen HT, Olsen J. Use of cephalosporins during pregnancy and in the presence of congenital abnormalities: a population-based, case-control study. Am J Obstet Gynecol 2001;184(6):128996. [Medline]
- Pastuszak A, Andreou R, Schick B, Sage S, Cook L, Donnenfeld A, et al. New postmarketing surveillance data supports a lack of association between quinolone use in pregnancy and fetal and neonatal complications. Reprod Toxicol 1995;9(6):584. [Google Scholar]
- Loebstein R, Addis A, Ho E, Andreou R, Sage S, Donnenfeld AE, et al. Pregnancy outcome following gestational exposure to fluoroquinolones: a multicenter prospective controlled study. Antimicrob Agents Chemother 1998;42(6):13369. Abstract/Full Text Article
- US Department of Health and Human Service, US Food and Drug Administration. Mercury levels in commercial fish and shellfish. Silver Spring, MD: US Food and Drug Administration; 2009. Available from: www.cfsan.fda.gov/~frf/sea-mehg.html. Accessed 2009 Feb 15.
- Spika JS, Shaffer N, Hargrett-Bean N, Collin S, MacDonald KL, Blake PA. Risk factors for infant botulism in the United States. Am J Dis Child 1989;143(7):82832. Erratum in: Am J Dis Child 1990;144(1):60. Abstract/Full Text
- Cox N, Hinkle R. Infant botulism. Am Fam Physician 2002;65(7):138892. [Medline]
- Cherington M. Clinical spectrum of botulism. Muscle Nerve 1998;21(6):70110. [Medline]
- Shapiro RL, Hatheway C, Swerdlow DL. Botulism in the United States: a clinical and epidemiologic review. Ann Intern Med 1998;129(3):2218. CrossRef
- Sobel J. Botulism. Clin Infect Dis 2005;41(8):116773. Epub 2005 Aug 29. [Abstract/Free Full Text]
- Robin L, Herman D, Redett R. Botulism in a pregnant women. N Engl J Med 1996;335(11):8234. CrossRef