Supplementation of the B vitamin folic acid in women before conception and during early pregnancy has been shown to reduce the occurrence of neural tube defects (NTDs) by at least 50-70%. This collective evidence has led to a number of activities around prevention of NTDs. In 1992, the U.S. Public Health Service recommended that women of childbearing age consume 400 micrograms of folic acid per day for the purpose of reducing their risk of having a pregnancy affected by an NTD. Subsequently, in 1996, the U.S. Food and Drug Administration made it optional to fortify enriched grain products with folic acid, and mandated fortification by 1998. Since 1995, the March of Dimes has commissioned Gallup to conduct surveys to measure women's awareness and behavior relative to folic acid and other pre-pregnancy health issues.