Robin Elise Weiss, LCCE, has written a comprehensive guide for foods to avoid during pregnancy:

Salmonella
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.

Listeriosis
Food most likely to be infected by listeria are unpasteurized milk products, improperly cooked meats, cooked chilled food, 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 and stillbirths have been linked to listeriosis infections spread by the mother to the unborn baby.
 

Additional tips:

• 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