the increased dosage of folic acid or folates reflects the american dietetic associations position that women should consume “400 μg per day of synthetic folic acid from fortified foods (cereals and other grains), supplements or both, in addition to consuming folate from foods in a varied diet.” taking the appropriate amount of folic acid before conception can reduce or prevent the incidence of neural tube defects by as much as 70%. the recommendation to start folic acid before conception is supported by a meta-analysis of 41 studies, but is beneficial after conception as well. often prenatal vitamins also have a reduced dosage of vitamins that may be detrimental to the fetus when taken in high doses (such as vitamin a).