Listeria is a type of bacteria which is widespread in the environment and has been found in water, soil and raw foods such as poultry and certain types of cheeses. The department of health confirm that the disease caused, by this bacteria, listeriosis, is rare, but the numbers of cases are increasing. However, only a handful of cases have been directly attributed to eating contaminated food. Listeria is a potential hazard in chilled food as unlike other food poisoning bacteria such as salmonella, it can survive and grow at refrigeration temperatures as low as 5°C (41°F).

Research at King's College and Queen Charlotte's hospitals has shown that pregnant women are susceptible to listeria infection and risk passing it on to their unborn baby. It is believed that a significant number of miscarriages and stillbirths may be caused by listeria infection and recent research suggests that listeria infection is the third most common cause of septicaemia (blood poisoning) and meningitis in the new-born.

What you can do:

All dairy products are important sources of calcium which is needed for the healthy growth and development of your baby. However, cheeses such as Brie, Camembert, Dolcelata and goat's cheeses should be avoided. Hard cheeses e.g. Cheddar, Cheshire, processed and cottage cheeses, yoghurt and pasteurised milk can be taken and will make a valuable contribution to your calcium intake.

"Ready to eat" cook chilled foods purchased from supermarkets such as cooked poultry and prepared packaged salads, especially those which are cabbage based, should be avoided. It is also important to avoid foods which are outside their "best before" or "eat within" date.

Cooking foods thoroughly will destroy listeria and make the food safe to eat. If you use a microwave, be sure to follow cooking instructions carefully; standing times are very important as they allow time for heat to penetrate evenly to all parts of the food. it is advisable to purchase a microwave thermometer to ensure temperatures exceed 90°C (194°F) in all parts of the food.

When purchasing chilled foods, buy them at the end of your shopping trip and bring them straight home and put them quickly into your refrigerator. It is important to make sure your fridge is working properly and keep the food at temperatures less than 5°C (41°F) by checking with a fridge thermometer.