It is highly advisable to avoid consumption of sushi during pregnancy. During pregnancy, women produce increased levels of progesterone which lowers cell mediated immune function1,2. Reduced immunity increases the risk of infection by foodborne pathogens, which may have dire consequences for the mother and foetus, increasing the risk of birth defects, miscarriage, premature labour and stillbirth1. Listeria monocytogenes and Salmonella are the most important food borne pathogenic bacteria to be aware of during pregnancy1,3. Foods at higher risk of contamination by these pathogens include: raw and cold cooked meats, such as chicken and beef; pre-prepared salad vegetables; raw and cold cooked seafood, such as oysters, prawns and fish; soft cheeses, such as camembert and feta; and raw egg and raw egg products, such as mayonnaise4. All ingredients which are commonly found in sushi.
Sushi is considered a potentially hazardous food5-7, as it contains highly perishable ingredients and undergoes significant manual handling during preparation5, increasing the risk of pathogenic bacterial growth. As a potentially hazardous food, businesses are required to maintain the temperature of sushi at or below 5˚C during transport, storage and display, in accordance with Standard 3.2.2 of the Food Standards Code5,6. The temperature range between 5˚C to 60˚C is referred to as the temperature danger zone for food4,8. Within this range, bacteria which causes food poisoning can multiply to unsafe levels, increasing the likelihood illness4,8. However, many businesses report that refrigeration compromises the quality and taste of the product, causing the sushi to dry out, become crunchy and lose flavour5. For this reason, businesses are able to adopt the “4 hour/2 hour rule” as an alternative compliance method under Clause 25 of Standard 3.2.25,6. This allows sushi products to be displayed outside of a temperature controlled environment for up to 4 hours. If displayed for less than 2 hours, the product may be returned to refrigeration; if displayed for between 2 and 4 hours, the product must be consumed immediately; beyond 4 hours on display, the product must be disposed of5-7. The NSW Food Authority conducted a study to assess the growth patterns of bacteria found in sushi products stored in unrefrigerated display cabinets and concluded that sushi must not be displayed at temperatures above 25°C, due to the dangerous growth of pathogenic bacteria beyond this temperature6.
Growth of food borne pathogens may also be promoted by the pH of sushi and its individual ingredients5-7,9. Sushi ingredients, such as rice, seafood and meat, are considered high-risk foods for pathogenic bacteria due to their neutral pH and high moisture, starch and/or protein content9. Adequate acidification of sushi rice through the addition of vinegar, to a pH less than or equal to 4.6, inhibits bacterial growth within the rice, but does not significantly reduce the pH, and subsequent bacterial growth, of other ingredients5.
An additional consideration with fish based sushi products is the risk of mercury exposure. Mercury may affect healthy development of the fetal nervous system4,9. Some seafood commonly used in sushi preparations, such as sea bass, tuna, mackerel, marlin and swordfish, are known to contain high levels of mercury9. Pregnant women are advised to consume no more than one serve of these fish per fortnight, with no other fish consumed during that time9.
Current Australian guidelines recommend pregnant women do not eat store bought sushi4,10. Homemade sushi is safe to consume if prepared with fresh ingredients in a clean environment, but must not contain raw meat or seafood, and must be consumed immediately10.
Smith JL. Foodborne infections during pregnancy. J Food Prot [internet]. 1999 Jul [cited 2017 Mar 20];62(7):818-29. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10419281?dopt=Abstract
NSW Food Authority. Listeria and pregnancy: the foods you should avoid and why [internet]. NSW: NSW Food Authority; 2014 Jan [cited 2017 Mar 20]. Available from: http://www.foodauthority.nsw.gov.au/_Documents/foodsafetyandyou/listeria_and_pregnancy.pdf
Tam C, Erebara A, Einarson A. Food-borne illnesses during pregnancy: prevention and treatment. Can Fam Phys [internet]. 2010 April [cited 2017 Mar 21];56(4):341-3. Available from: http://www.cfp.ca/content/56/4/341.full#ref-1
Food Standards Australia New Zealand. FSANZ Website [internet]. Barton: FSANZ; 2015 [cited 2017 Mar 21]. Available from: http://www.foodstandards.gov.au
NSW Food Authority. Report on food handling practices and microbiological quality of sushi in Australia [internet]. NSW: NSW Food Authority; 2008 Jul [cited 2017 Mar 21]. Available from: http://www.foodauthority.nsw.gov.au/_Documents/scienceandtechnical/report_quality_sushi_australia.pdf
NSW Food Authority. Food safety guidelines for the preparation and display of sushi [internet]. NSW: NSW Food Authority; 2007 Jun [cited 2017 Mar 21]. Available from: http://www.foodauthority.nsw.gov.au/_Documents/retail/sushi_preperation_display_guidelines.pdf7w
Food Standards Australia New Zealand. A guide to the food safety standards [internet]. 3rd edn. Barton: FSANZ; 2016 Nov [cited 2017 Mar 21]. Available from: https://www.foodstandards.gov.au/publications/Documents/Safe%20Food%20Australia/Appendix%204%20-%20Foods%20requiring%20special%20care.pdf
Food Safety Information Council. FSIC Website [internet]. Kingston: FSIC; [date unknown] [cited 2017 Mar 21]. Available from: http://foodsafety.asn.au/
Australian Institute of Food Safety. AIFS Website [internet]. Brisbane: AIFS; [date unknown] [cited 2017 Mar 21]. Available from: https://www.foodsafety.com.au/
NSW Food Authority. NSW Food Authority Website [internet]. NSW: NSW Food Authority; 2015 Dec [cited 2017 Mar 21]. Available from: http://www.foodauthority.nsw.gov.au