During the last decade critical new information has been published pertaining to folic acid supplementation in the prevention of neural tube defects (NTDs) and other folic acid-sensitive congenital malformations. These new data have important implications for women, their families, and health care professionals. We performed a review looking for the optimal dosage of folic acid that should be given to women of reproductive age who are planning or not avoiding conception to propose updated guidelines and thus help health care providers and patients. In addition to fortification of dietary staples with folic acid, women of reproductive age should supplement before conception with 0.4-1.0 mg of folic acid daily as part of their multivitamins. In the United States all enriched rice is also fortified with folic acid at 0.7 mg per pound of raw rice. However, this is not the case in many countries, and it has been estimated that only 1% of industrially milled rice is fortified with folic acid. In countries where rice is the main staple (eg, China), this does not allow effective folate fortification. Whereas the incidence of NTDs is around 1/1000 in the United States, it is 3- to 5-fold higher in Northern China and 3-fold higher in India. A recent population-based US study estimated that the reduction in NTD rates by folic acid is more modest than previously predicted. The potential of NTD prevention by folic acid is underutilized due to low adherence with folic acid supplementation, and calls for revising the policy of supplementation have been raised. We identified groups of women of reproductive age who may benefit from higher daily doses of folic acid, and this should be considered in current practice. These include women who have had previous pregnancies with NTDs, those who did not plan their pregnancy and hence did not supplement, and women with low intake or impaired adherence to daily folic acid supplementation. In addition, women with known genetic variations in the folate metabolic cycle, those exposed to medications with antifolate effects, smokers, diabetics, and the obese may benefit from higher doses of folic acid daily during the first trimester.