The U.S. Preventive Services Task Force (USPSTF) recommends that all women who are planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 µg) of folic acid. This is an A recommendation, which means the USPSTF recommends the service. There is high certainty that the net benefit is substantial.
U.S. Preventive Services Task Force. Folic Acid for the Prevention of Neural Tube Defects: Preventive Medication [Internet]. 2017 Jan [cited 2017 Sept 8]. Available from: https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/folic-acid-for-the-prevention-of-neural-tube-defects-preventive-medication?ds=1&s=Folic%20Acid%20to%20Prevent%20Neural%20Tube%20Defects