INTRODUCTION
Folate (vitamin B9) is an essential nutrient, important in DNA and RNA synthesis, DNA methylation, hematopoiesis, and possibly normal neuronal function. Folic acid supplementation is recommended for all females capable of becoming pregnant, particularly those planning to conceive, because, in addition to its other physiologic functions, periconceptional use decreases the occurrence and recurrence of fetal neural tube defects (NTDs). Preconception patient education about the need for supplementation is important during medical wellness visits as many patients are not aware of this recommendation until after they seek prenatal care or they choose not to follow the recommendation because of cost or inconvenience [1,2]. Individuals who do not take supplements still consume some folate since it is a natural component of a variety of foods, and grain products in many countries are fortified with folic acid.
This topic will discuss the role of folic acid supplementation for prevention of NTDs, dosing in females at low versus increased risk of NTDs, potential pregnancy benefits unrelated to NTDs, potential risks of supplementation, and why NTDs occur despite supplementation. Prenatal screening and diagnosis of NTDs are reviewed separately. (See "Neural tube defects: Overview of prenatal screening, evaluation, and pregnancy management".)
FOLATE AND FOLIC ACID
Although the terms folate and folic acid are often used interchangeably, folate is a water-soluble B vitamin (B9) that occurs naturally in foods, whereas folic acid is the synthetic form of folate.
Sources
●Pharmacologic sources – Folic acid is available in multivitamins, prenatal vitamins, and as a pure folic acid supplement. It has also been added to some oral estrogen-progestin contraceptive pills to ensure adequate baseline folate levels in the event of unplanned pregnancy from inconsistent/incorrect contraceptive use or from conception soon after contraceptive discontinuation.
Calcium and glucosamine methylfolate salts are metabolically active forms of folic acid that are included in some supplements instead of folic acid.