Listeria is a bacteria that is found in nature and lives in some foods. Sources of Listeria include most animals, soil, vegetation and sewerage. Because of this, Listeria can easily enter our food chain. An infection with Listeria can cause mild ‘flu-like’ symptoms, urinary tract infections or even quite serious illness. In adults who have an impaired immune system, Listeria can cause illnesses such as meningitis, pneumonia and encephalitis. The bacteria that causes Listeria is called Listeria monocytogenes. In pregnancy, this bacteria can pass across the placenta and reach the baby. Listeria during pregnancy can cause abortion, premature rupture of membranes, premature birth and very sick babies. Listeria infections are not new, however we have only known since the 1980’s that it can be passed onto humans through food.
An infection with Listeria can be easily missed as it often presents with vague symptoms. A blood test or a test on the amniotic fluid can identify a Listeria infection. Listeria can be treated with certain antibiotics. If a baby contracts a Listeria infection it can become extremely sick with respiratory problems or meningitis. The baby can even die. Listeria infection is quite rare in Australia, but when it occurs in pregnancy it can have serious complications. It is for this reason that information is now available to pregnant women, so that they can make safe choices on the foods to eat during pregnancy.
The bacteria that causes Listeria is sensitive to heat. So by cooking food well, you are able to destroy it. When cooking meats ensure that the meat is cooked right through. Rare meat is not recommended. If you use the microwave to reheat, ensure that the food is steaming hot right through to the centre. While heat destroys Listeria, refrigeration does not. Listeria is one of the few bacteria that are able to grow on food in the refrigerator. So if food has been stored for longer than twelve hours after cooking – it is best that you do not eat it. Also avoid chilled ready to eat foods.
What steps can I take at home to avoid the risk of catching Listeria in my pregnancy?
The best way to avoid Listeria is by using good food hygiene. The first step is washing your hands before preparing any food. Raw fruit and vegetables should be thoroughly washed before eating. Food should be well cooked; no raw or partially cooked meats and seafood should be eaten in pregnancy. Food should be served piping hot. Do not eat lukewarm food. If using the microwave ensure that the food is well heated through to the centre.
Hot soapy water should used to wash all food utensils. It is particularly important to wash chopping boards and knives after preparing raw food. Proper storage of food is essential. Store all your cooked food separately from uncooked products. Make sure that the raw food cannot drip onto cooked food. If you have cooked leftovers, place them straight into the fridge once they have stopped steaming (do not let food cool on the bench). Use all left overs within 12 hours of cooking or alternatively freeze for later use. Ensure that cooled food is kept below 5 degrees Celsius. Also do not eat food that has passed its used by date.
My partner and I eat out a lot. I have heard that take away food is not safe in pregnancy. Is this true?
It is important to be careful when buying take-away food. If it is fresh and piping hot it is safe to eat. If it is lukewarm – avoid it. A lot of takeaway food is cooked and then stored under warming lights until it purchased. It is wise to avoid this type of food. Salad bars and smorgasbords should be avoided if possible. If having to eat from a smorgasbord, choose from the hot food only. By being careful when eating out, you can reduce the risk of eating foods that may be contaminated with Listeria. Do not eat food if you are uncertain about the preparation and/or storage of the food. If you are sensible you can continue to enjoy eating out.
What foods should I avoid in pregnancy?
There are certain foods that are considered to be of high risk of Listeria contamination. The foods to avoid in pregnancy include:
- Soft white cheeses eg. Ricotta, brie, camembert, blue vein and fetta
- Unpasturised dairy products
- Cold meats
- Dried/fermented sausages
- Raw seafoods eg. Oysters, sashimi
- Smoked seafood (canned is okay)
- Pre packed and prepared salads
- Soft serve ice-cream
What foods are safe to eat in pregnancy?
Freshly prepared and freshly cooked foods are the safest. It is important to eat a well balanced diet that contains plenty of fresh fruit and vegetables, breads, cereals, meat, fish, eggs, lentils and nuts. Ensure meat is well cooked. All hot food should be piping hot. The following foods are safe to eat in pregnancy:
- Washed fruit and vegetables
- Home made salads
- Hard Cheese
- Processed cheese
- Canned foods
- All meats – thoroughly cooked, hot and fresh
- Pasteurised diary products
- Australian New Zealand Food Authority. (?). [Listeria and pregnancy]. Brochure.
- Bennett, V. R., & Brown, L. K. (Eds.). (1993). Myles textbook for midwives (12th ed.). London: Churchill Livingstone.
- Beth (surname unknown). (2000, June). [Listeria Alert]. Ozmidwifery e-mail list.