Although the importance of folic acid in pregnancy seems to be well known today, there is still a high percentage of women who are unaware of it. Due to this fact, the US Preventive Services Task Force published in January 2017 a recommendation statement in The Journal of the American Medical Association (JAMA). This recommendation reaffirms the 2009 recommendation statement on folic acid supplementation in women of childbearing age. The current statement recommends that all women who are planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400-800 µg) of folic acid. Randomized and observational studies suggest that taking folic acid before and during pregnancy significantly decreases the risk of fetal neural tube defects.
Reference: JAMA. 2017;317(2):183-189