Eating a healthy diet during pregnancy is one of the best things you can do for yourself and your baby. After all, the food you eat is your baby's main source of nutrition. Smart choices about pregnancy nutrition can help you promote your baby's growth and development.

Grains

Grains provide essential carbohydrates, your body's main source of energy. Many whole-grain and enriched products also contain fiber, iron, B vitamins and various minerals. Fortified bread and cereal can help you get enough folic acid.

What to eat: Make sure at least half of your grains each day are whole grains. If that sounds like a lot, don't worry. It might not be as much as you think. You can get most of your day's grains with a bowl of fortified cereal for breakfast, a lunchtime sandwich made with two slices of whole-wheat bread and whole-wheat pasta for dinner.

To optimize pregnancy nutrition, trade sugary cereals and white bread for whole-grain cereals, brown rice, whole-wheat pasta and whole-grain bread. Try wild rice or barley in soups, stews, casseroles and salads. Look for products that list whole grains, such as whole-wheat flour, first in the ingredients list.

Fruits and vegetables

Fruits and vegetables are critical components of pregnancy nutrition, since they provide various vitamins and minerals, as well as fiber to aid digestion. Vitamin C, found in many fruits and vegetables, helps you absorb iron. Dark green vegetables have vitamin A, iron and folate — other important nutrients during pregnancy.

What to eat or drink: Top your cereal with slices of fresh fruit. Make a veggie pizza. Add extra vegetables to your casserole.

If you're tired of apples, oranges and green beans, branch out. Try apricots, mangoes, pineapple, sweet potatoes or spinach.

Meat, poultry, fish, eggs and beans

Foods in this group have plenty of protein, as well as B vitamins and iron. Protein is crucial for your baby's growth, especially during the second and third trimesters.

What to eat: Try whole-wheat toast with peanut butter for breakfast. Eat a scrambled egg or an omelet for lunch. Add chickpeas or black beans to your salad. Snack on a handful of soy nuts.

If your traditional sources of protein no longer appeal to you — likely during the first trimester — experiment with other options. Fish is an excellent source of protein as well as omega-3 fatty acids, which can promote your baby's brain development.

Dairy products

The calcium in dairy products and calcium-fortified soy milk helps build your baby's bones and teeth. Dairy products also have vitamin D and protein.

What to eat or drink: Eat yogurt for your afternoon snack. Drink the milk in your cereal bowl. Have a glass of skim milk with dinner. Add low-fat cheese to a salad.

If you have trouble digesting dairy products, get creative. Try calcium-fortified orange juice or sardines. Experiment with lactose-reduced or lactose-free products. Use an over-the-counter lactase enzyme product when you eat or drink dairy products.

Water

Water carries nutrients from the food you eat to your baby. It can also help prevent constipation, hemorrhoids, excessive swelling, and urinary tract or bladder infections. As your pregnancy progresses, drinking too little water can contribute to premature or early labor.

How much: The Institute of Medicine recommends about 10 cups (2.4 liters) of fluids a day during pregnancy. Water, juices, coffee, tea and soft drinks all contribute to your daily fluid needs. Keep in mind, however, that some drinks are high in sugar and too much can cause weight gain. Because of the potential effects on your developing baby, your health care provider might also recommend limiting the amount of caffeine in your diet to less than 200 milligrams a day during pregnancy.

Fats, oils and sweets

There are no minimum requirements for fats and sweets. Choose foods with healthy fats such as nuts, seeds or avocados. Use oil and vinegar as your salad dressing. It's OK to indulge once in a while — as long as you're getting the nutrients you need and your weight gain is on target. To avoid going overboard, control your portion sizes of foods high in fat and sugar.

Ask about supplements

Even women who eat healthfully every day can miss out on key nutrients. A daily prenatal vitamin — ideally starting three months before conception — can help fill any gaps. Your health care provider might recommend special supplements if you follow a strict vegetarian diet, or have any chronic health conditions, such as diabetes. Always consult your health care provider before taking any new vitamins or supplements during pregnancy.

Twins or other multiples

If you're pregnant with twins or other multiples, you'll likely need more nutrients and calories than does a woman pregnant with one baby. Consult your health care provider about how much more to eat.