In 1999 the American Academy of Pediatrics endorsed the U.S. Public Health Service recommendation that all women capable of becoming pregnant consume 400 micrograms of folic acid daily to prevent neural tube defects.

The academy also supports the recommendation of the Centers for Disease Control and Prevention for women who have previously had an NTD-affected pregnancy; these women should consume 4000 micrograms of folic acid per day, beginning at least one month before conception and continuing through the first trimester.

Source: Committee on Genetics, American Academy of Pediatrics. Folic acid for the prevention of neural tube defects (RE9834). Pediatrics, volume 104, number 2, August 1999, pages 325-327.