Vitamins Folic Acid

Maternal folate requirements increase markedly during pregnancy due to the utilization of the vitamin in cell division in the mother and fetus, single-carbon transfer reactions, and deposition in the fetus. Approximately a decade ago, research including randomized controlled trials finally proved that the risk of women giving birth to an infant with a neural tube defect (NTD) was significantly reduced if they consumed folic acid supplements prior to conception through approximately the first 4-6 weeks of pregnancy—during the time of neural tube closure. Some women are at greater risk of producing an infant with this birth defect, especially when their folate intake is rather low. Because such women are unaware of this risk unless they have had a previous NTD delivery, the recommendation is that all women who are capable of becoming pregnant consume at least 400 mg of folic acid daily from supplements, fortified food, or both in addition to consuming food folate from a varied diet.

In pregnancy, the recommendation is for all women to consume an additional 200 mg dietary folate equivalents daily (approximately 100 mg of folic acid as a supplement, which is more than twice as bioavailable as folate in food) in addition to the RDA for the nonpregnant woman of 400 mg/day. This amount was shown to prevent plasma homocysteine from becoming elevated during pregnancy and to maintain normal folate concentration in red blood cells. The UL of 1000 mg/day, the same as for nonpregnant women, is set to avoid potential exacerbation of vitamin B12 deficiency.

In the United Kingdom, the recommendation is substantially lower—an intake of 100 mg folate daily in addition to the recommendation of 200 mg/day for the nonpregnant, nonlactating woman. The UK committee's recommendation was based on the assumption that 100 mg/day will maintain plasma and erythrocyte folate concentrations at least at the level of those of nonpregnant women. Prevention of NTDs was not discussed, probably in part because the results of folic acid intervention trials were not clear at the time the recommendations were set.

In addition to its importance for lowering risk of NTDs in the periconceptional period, there is evidence that adequate folate status, which is important for maintaining normal plasma homocysteine concentrations, lowers the risk of other delivery problems and birth defects, including preeclampsia, preterm delivery, very low birth weight, club foot, and placental abruption. In the United States, Canada, and many other countries (more than 20 in Latin America alone), wheat flour is fortified with folic acid to ensure adequate folate status for pregnant women.

Pregnancy And Childbirth

Pregnancy And Childbirth

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