From Robin Elise Weiss, LCCE,Your Guide to Pregnancy / Birth.
It seems like every time you turn around someone is telling pregnant women to avoid something. Unfortunately food preparation is included in the list of cautions. However, with a few simple rules you can have a carefree and safe pregnancy.
Most pregnant women know that they are to avoid or minimize things that have little or no nutritional value, like caffeine, sweets, processed foods, etc.. However, there are some things that also need to be watched for in general:

This is usually traceable to eggs and chicken meat. This means no more licking the cake batter spoon! You should always ensure that your eggs and meats are cooked thoroughly. When using a cutting board for chicken be sure to wash it prior to using it for another food, particularly things like raw vegetables.
Symptoms can include: headache, abdominal pain, nausea, diarrhea, shivering or fever. Usually symptoms occur within 12-48 hours after infection and lasts about 2-3 days. Only if it is severe will treatment usually be necessary. Though if you’re vomiting and become dehydrated IV therapy may be beneficial.
Food most likely to be infected by listeria are unpasteurized milk products, improperly cooked meats, cooked chilled food (luncheon meat being the most recent scare), soft cheese are some of the major players. Normally this bacteria is killed at the pasteurizing temperature, but if the food is refrigerated after being infected the bacteria is still present. Rarely, but still possible for some, is transmission through direct contact with live stock.
General aches and pains accompanied by a fever are the main symptoms. Usually people think that they have the flu. Reports of miscarriage (including recurrent) and stillbirths have been linked to listeriosis infections spread by the mother to the unborn baby.
Never eat raw meat or eggs
Always wash your hands after preparing food, between foods, and after the restroom
Avoid contaminating foods with each other
Always use clean utensils and cooking equipment
Avoid dented cans
Eat or drink only pasteurized products, including apple juice
Completely defrost foods, especially meats, prior to cooking
Do not refreeze anything that has been defrosted
Reheat food only once, then toss it