Essential nutrients when you're eating for two. A balanced diet is the key to pregnancy nutrition. When you're pregnant, eat foods packed with these nutrients. There's no magical formula for pregnancy nutrition. In fact, during pregnancy the basic principles of healthy eating remain the same — plenty of fruits, vegetables and whole grains and lean sources of protein. However, a few nutrients do deserve special attention . Here's what tops the list.

Folate and folic acid Folate is a B vitamin that helps prevent neural tube defects, serious abnormalities of the brain and spinal cord. Lack of folate also may increase the risk of preterm delivery, low birth weight and poor fetal growth. The synthetic form of folate found in supplements and fortified foods is known as folic acid.

How much you need: 1 milligram (1,000 micrograms) of folate or folic acid a day before conception and during pregnancy.

Good sources: Fortified cereals are great sources of folic acid. Leafy green vegetables, citrus fruits, and dried beans and peas are good sources of naturally occurring folate.

- Food Serving size Folic acid content - Cereal 3/4 cup 100 percent fortified ready-to-eat cereal 400 micrograms - Meat 3 ounces beef liver 185 micrograms - Spinach 1/2 cup boiled spinach 100 micrograms - Beans 1/2 cup boiled Great Northern beans 90 micrograms - Asparagus 4 spears boiled asparagus 85 micrograms - Oranges 1 small orange 30 micrograms

Source: USDA National Nutrient Database for Standard Reference

In addition to healthy food choices, a daily prenatal vitamin — ideally starting three months before you get pregnant — can help ensure you're getting enough of this essential nutrient.

CalciumYou and your baby need calcium for strong bones and teeth. Calcium also helps your circulatory, muscular and nervous systems run normally. If there's not enough calcium in your diet, the calcium your baby needs will be taken from your bones.