Folic acid is a vitamin essential for preventing birth defects and premature births—and, as new research shows—it's especially important to take long before you plan to get pregnant.

Why do I need folic acid before I even try to get pregnant?

Sure, you know you need to take prenatal vitamins during pregnancy. But new research from the University of Texas Medical Branch at Galveston reveals that taking folic acid (it's found in multivitamins and prenatal vitamins) for at least a year before conceiving may reduce the risk of preterm birth by 50 to 70 percent. About 13 percent of babies are born prematurely every year.

"Half of all pregnancies in the U.S. are unplanned," says Diane Ashton, MD, deputy medical director for the March of Dimes. "So it's important that all women of child-bearing age take folic acid supplements every day—just to be safe—even if they're not trying to get pregnant just yet." Folic acid also plays a big role in preventing birth defects of the brain and spinal cord early in the first trimester—before many women even know they're pregnant.

How much folic acid do I need?

Women should get 400 micrograms every day before and while they're trying to conceive, says Dr. Ashton. Once you know you're pregnant, you should increase your intake to at least 600 micrograms a day. (Many regular women's multivitamins contain 400 micrograms per tablet; prenatal supplements usually contain 800 to 1,000 micrograms of folic acid per tablet.)

Do I really need a vitamin or can I get folic acid from my diet?

Although many foods contain folate (the natural form of folic acid) or are fortified with folic acid, it's hard to get enough from diet alone, says Dr. Ashton. Folate-rich foods include dark leafy veggies like broccoli and brussels sprouts, as well as beans, legumes, and oranges. And since 1998, the U.S. Food and Drug Administration has required that bread, cereal, rice, and pasta be fortified with folic acid.

While these foods are an important part of a healthy, balanced diet, eating them in conjunction with a multivitamin or prenatal vitamin is your best bet. "Taking a daily multivitamin is like a good insurance policy," Dr. Ashton says, ensuring that you get enough of the nutrient every day regardless of what you eat. Plus, research from the Institute of Medicine has shown that your body absorbs folic acid better from supplements than from food.