A record 40% of American women of childbearing age reported taking a daily multivitamin containing folic acid in 2004, up from 32% last year and the highest level since the March of Dimes began surveying women in the 1990s, according to the organization's latest survey, which was published in Morbidity & Mortality Weekly Report.

"Frankly, we're surprised at this increase, but it's good news," says Dr. Jennifer L. Howse, president of the March of Dimes. "The increase is especially important because we've been very worried about the effects on mothers and babies of popular low-carbohydrate diets that drastically reduce grain foods enriched with folic acid, such as bread and pasta. However, our survey finds that 49% of women who have been on low-carb diets in the past six months said they actually took a daily multivitamin containing folic acid. So, perhaps these women are taking their vitamins because they realize they're missing out on important food groups."

However, Howse said, low-carb and other diets could not be the only reason behind the increase, because rates of folic acid use were also higher than expected for women not dieting (39%). She also said the March of Dimes urges all women to eat a varied, healthy diet before and during pregnancy.

Of women who were not pregnant at the time of the 2004 survey, 37% reported taking a vitamin containing folic acid daily, up from 30% in 2003.

Daily consumption of the B vitamin folic acid beginning before pregnancy is crucial, the report noted, because serious birth defects of the brain and spine known as neural tube defects (NTDs) occur in the early weeks following conception, often before a woman knows she is pregnant.

The survey was conducted for the March of Dimes by The Gallup Organization under a grant from the U.S. Centers for Disease Control and Prevention.

Howse said the March of Dimes survey found that more women seem to understand the importance of folic acid to the health of babies. A comparison of the eight previous surveys shows that 12% of women know that, to be effective, folic acid must be consumed before pregnancy -- up from only 2% in 1995. Those who know that folic acid helps prevent birth defects increased to 24% in 2004, up from only 4% in 1995.

"Although folic acid now has a higher profile in this country, we can't be complacent in our efforts to prevent disabling or fatal NTDs from occurring," said Howse. "We urge health care professionals and pharmacists to remember to use every contact they have with women capable of having a baby to advise them to take a multivitamin with at least 400 micrograms of folic acid daily."

NTDs are among the most serious birth defects in the United States. Each year, an estimated 2,200 babies are born with these defects, and additional affected pregnancies result in miscarriage or stillbirth. To help prevent NTDs, the March of Dimes says, all women capable of becoming pregnant should consume a multivitamin containing at least 400 micrograms of folic acid every day beginning before pregnancy, as part of a healthy diet containing foods fortified with folic acid and foods that naturally contain folic acid, such as leafy green vegetables, and beans.

The March of Dimes 2004 survey results are based on telephone interviews with a national sample of 2,012 women age 18 to 45 conducted from April 19 to May 20, 2004. For results based on samples of this size, one can say with 95% confidence that the error attributable to sampling and other random effects could be plus or minus three percentage points.