The most important thing for a mother is to make sure and eat a healthy, well balanced diet, that is not composed of too much junk food or too many fatty foods. It is also important to make sure and eat plenty of fruits and vegetables, not just for your baby's health, but also for your own. With regards to your baby, there are some foods that should be avoided that your obstetrician or midwife will discuss with you. Some soft cheeses (and unpasteurized dairy products as well) can contain some bacteria that can be harmful, and are to be avoided.
Additionally, there are some types of sea food that have high levels of mercury, and it is generally recommended to avoid these as well. Again, your primary health care provider during this time can provide you with lists of what to avoid. As for what to eat, high fiber will help you to feel better during pregnancy, as it will help you to avoid constipation, which is a common pregnancy complaint. Otherwise, what is healthy for you is generally healthy for your baby. Please discuss this question with your obstetrician, and please remember to take a prenatal vitamin as well.