Foods to avoid in pregnancy
During pregnancy, certain bacteria in food (such as Listeria and Salmonella), or parasites such as Toxoplasma gondii) can be extremely harmful to the developing foetus. Therefore some foods need to be avoided during pregnancy, and good food preparation and hygiene practices are particularly important in order to prevent potentially harmful foodborne illnesses.
Listeria monocytogenes is a pathogenic bacterium which causes a group of diseases collectively known as Listeriosis. Listeriosis in pregnancy is characterised by diarrhoea, headache, fever, muscle pain, meningitis, septicaemia, as well as spontaneous abortion.
Listeria monocytogenes can grow at refrigeration temperatures but is killed by cooking and pasteurisation. Therefore, unpasteurised milk and unpasteurised dairy products are not recommended during pregnancy. Some refrigerated foods with a long shelf life (greater than 5 days) which are consumed without further cooking also have a high risk of contamination since L. monocytogenes can grow at refrigeration temperatures.
Toxoplasmosis is caused by the bacterium Toxoplasma gondii and infection is caused by ingestion of Toxoplasma oocytes excreted in cat faeces, or by eating raw or under cooked meat with visible cysts. Infection with this bacterium during pregnancy can result in the transfer of the bacterium to the foetus and result in spontaneous abortion or serious handicap in the newborn.
Raw or undercooked meats, poorly fermented or cured meats, and unwashed fruit and vegetables are potential sources of this bacterium and should be avoided during pregnancy.
Meat should be well cooked (no pink meat) and served piping hot to prevent Toxoplasma gondii infection. Hand washing (especially after handling raw meat and unwashed vegetables) and other hygiene practices are of utmost importance as well as wearing gloves when gardening or changing cat litter.
Salmonella and Campylobacter
While Salmonella or Campylobacter infection is unlikely to cause any problems with a pregnancy or with foetal development, it’s very unpleasant to suffer the effects during pregnancy. Pregnant women are advised to take steps to minimise the risk of infection: cooking eggs till the yolk and white are solid and avoiding products that may contain raw egg, such as homemade mayonnaise (shop bought mayonnaise is acceptable due to it not containing raw egg).
There are some other considerations for foods to avoid during pregnancy outlined below.
Liver, liver products and supplements containing vitamin A
Liver and liver products contain high levels of vitamin A . Very high amounts of vitamin A (greater than 7000ug per day) may harm the developing fetus. Consequently, pregnant women are advised to avoid liver and liver products1.
As some vitamin supplements contain high levels of vitamin A, pregnant women need to be careful about which type of supplement they take. A woman who wants to take a multi-nutrient supplement should be directed towards those specially formulated for pregnancy. Fish liver oils also contain high levels of vitamin A and should be avoided during pregnancy.
There is no known safe alcohol intake in pregnancy therefore the Department of Health and the Food Safety Authority of Ireland recommend that pregnant women avoid alcohol completely.
Alcohol is a teratogen (a substance which is harmful to the developing foetus), and can easily pass through the placenta to the developing foetus. Alcohol consumption during pregnancy can lead to the development of Foetal Alcohol Syndrome which is characterised by behavioural problems, mental retardation, aggressiveness, nervousness, short attention span, growth retardation, and birth defects4. The negative effects of maternal alcohol consumption on a developing baby seem to occur at widely varying alcohol intakes. This makes it hard to justify a ‘safe’ alcohol intake during pregnancy1.
Shark, swordfish and marlin
Concerns about high levels of mercury have led to a recommendation to avoid eating shark, swordfish and marlin during pregnancy. Mercury at high levels can damage the developing nervous system1.
Oysters and mussels
Oysters and mussels should be completely avoided in pregnancy, as they may contain biotoxins which are not destroyed during cooking2.
Due the mercury content of tuna, pregnant women should limit their intake of tuna to one fresh tuna steak (150g) per week or two 240g tins of tuna per week1.
In the past, it was recommended that mothers of infants at high risk of developing atopic disease (infants with at least 1 first degree relative with an allergy) should avoid potentially high allergenic foods during pregnancy including eggs, cow’s milk, fish, peanuts, and tree nuts. However, the most recent guidelines by the Food Safety Authority of Ireland state that unless the mother is allergic to the food herself, there is no evidence to recommend the elimination of these foods from her diet1.
The Food Safety Authority of Ireland recommends that pregnant women should not have more than 200mg/day of coffee1 (approximately 2 cups of brewed coffee per day).
Foods to avoid1
- Vitamins and other supplements, including fish liver oil supplements, which contain vitamin A (or retinol)
- Liver and liver products
- Milk that has not been pasteurised or ultra-heat treated
- Dairy products made with unpasteurised milk including all soft cheese and mould-ripened cheese (even those made with pasteurised milk), e.g. Brie, Camembert, Goat’s cheese, and blue cheese, e.g. Danish Blue, Stilton, Roquefort.
- Pâté of any sort
- Uncooked and under-cooked ready-prepared meals
- Raw and partially cooked eggs and food that may contain them
- Raw meat products and partially cooked meat
- Uncooked cured or smoked meats
- Smoked salmon and gravid lax fish
- Soft-serve ice-cream
- Unwashed fruit and vegetables, including ready-prepared salads
- Raw shellfish
- Shark, swordfish and marlin
- Limit tuna to one fresh tuna steak (150g) per week or two 240g tins of tuna per week.
- Avoid alcohol completely during pregnancy.
- Unwashed fruit, vegetables & salad should be avoided. All fruit, vegetables and salads should be thoroughly washed before consumption, including pre-washed salad leaves
- Imported frozen berries. The FSAI advises that all imported frozen berries should be boiled for one minute before consumption
- Caffeine intake should be limited. Limit caffeine intake to less than 200mg per day
Food preparation and hygiene
- Always wash hands before handling food
- Wash fruit and vegetables thoroughly before eating
- Keep raw and cooked meats separate when cooking and when storing in the fridge
- Wash hands and chopping boards thoroughly after contact with uncooked meats.
- Use different kitchen utensils and chopping boards when cooking raw and cooked meats to avoid cross contamination
- Clean kitchen surfaces with disinfectant after preparing uncooked meat
- Cook all foods thoroughly especially meat and fish and serve hot
- Ensure the temperature of the fridge is <5°C
- Avoid eating foods past their ‘use by’ date
- Water from a contaminated supply should not be consumed. Check with your local authority that your tap water is safe for consumption.
- Drink bottled water only when abroad.
- Always wash hands:
- before preparing and eating foods
- before and after handling raw meat
- after contact with animals
- after going to the toilet or changing a baby’s nappy
- after gardening
- Food Safety Authority of Ireland (2012). Best Practice for Infant Feeding in Ireland.
- Food Safety Authority of Ireland (2019). Healthy eating, food safety and food legislation. A guide supporting the Health Ireland food pyramid.