The US Preventive Services Task Force (USPSTF) has reaffirmed its 2009 advice that all women who are planning or capable of pregnancy should take a daily supplement of folic acid of between 0.4mg and 0.8mg (400–800Âµg) to reduce the risk of having a baby with neural tube defects.
The reaffirmed recommendation follows a review of the benefits of folic acid supplements based on the results of one randomised clinical trial, two cohort studies, eight case controlled studies and two publications since the 2009 advice was first published.
The USPSTF says that the risk to the mother and unborn child of taking the daily supplement is small and that there is “convincing evidence” that the supplement — which should be taken in the month before conception and the following three months of pregnancy — “provides substantial benefits” in reducing the risk of neural tube defects in the developing foetus.
Writing in JAMA
(online, 10 January 2017), the USPSTF says: “The USPSTF assessed the balance of the benefits and harms of folic acid supplementation in women of childbearing age and determined that the net benefit is substantial.
“Evidence is adequate that the harms to the mother or infant from folic acid supplementation taken at the usual doses are no greater than small.”
The USPSTF recommendation has an A status, which means that there is a high certainty that the net benefit is “substantial”.
 US Preventive Services Task Force. Folic acid supplementation for the prevention of neural tube defects US Preventive Services Task Force recommendation statement. JAMA 2017;317(2):183-189. doi: 10.1001/jama.2016.19438