Because the neural tube closes in the first four weeks of gestation, often before many women even know they are pregnant, many countries in time decided to implement mandatory food fortification programs. A meta-analysis of global birth prevalence of spina bifida showed that when mandatory fortification was compared to countries with healthcare professionals advising women but no mandatory fortification program, there was a 30% reduction in live births with spina bifida, with some countries reported a greater than 50% reduction.Over 80 countries require folic acid fortification in some foods. Fortification of rice is common. The USDA has required the fortification of flour since 1998. Since then, Hispanics in the United States have seen the greatest reduction of neural tube defects. Canada has mandated folic acid fortification of flour since 1998 which has resulted in a 42% decrease in neural tube defects. Fortification of wheat and corn flour, milk and rice is required in Costa Rica which has led to a reduction of neural tube defects of as much as 60%. Epidemiology
Folate deficiency is very rare in countries with folic acid fortification programs. Overall, the worldwide prevalence of anemia due to folic acid deficiency is very low. However, data on the prevalence of deficiency amongst specific high risk groups is lacking.
Mutations of the SLC46A1 gene that encodes the proton-coupled folate transporter (PCFT) result in CFD syndromes with both systemic folate deficiency and cerebral folate deficiency. Even when the systemic deficiency is corrected by folate, the cerebral deficiency remains and must be treated with folinic acid. Pregnancy
Folate deficiency can occur during pregnancy as a result of the increasing number of cells of the growing fetus, decreased absorption and intake of folate, maternal hormones that mediate its metabolism, vascular circulation of maternal and fetal blood and an increasing amount of blood resulting in dilution. Sickle cell anemia and living in areas of malaria result in even higher folate needs for women who are pregnant. When supplemented with 450 micrograms of folic acid per day, the risk of developing birth defects, specifically neural tube defects, is decreased. Supplementation to prevent birth defects is most effective one month prior to and during the first twelve weeks of pregnancy. Utilization of folic acid supplementation before conception has shown to result in a decrease in neural tube defects by 70%. Diagnosis
Folate deficiency is diagnosed with a blood test to measure the serum level of folate, measured as methyltetrahydrofolate (in practice, "folate" refers to all derivatives of folic acid, but methylhydrofolate is the quasi unique form of "folate" in the blood). Homocysteine is elevated (5-MTHF is used to convert homocysteine to methionine) as in vitamin B12 deficiency, whereas methylmalonic acid is normal (elevated in vitamin B12 deficiency).