Folic Acid Requirements for Women in Pregnancy
Posted by Tom Craig in Pregnancy
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Folic acid requirements increase during pregnancy in response to the demands of maternal erythropoiesis and fetal and placental growth and, most important, for the prevention of NTDs. The RDA for folic acid in pregnancy is 600 mcg, a 200 mcg increase over that for nonpregnant females. The IOM recommends thlt 400 mcg of the 600 mcg/day be provided by folate-fortified foods or supplements because it is better absorbed, with 200 mcg from food and beverages. A tolerable upper intake level (UL) is 800 to 1000 mcg/day from fortified foods or supplements.
Folic acid deficiency is marked by a reduced rate of deoxyribonucleic acid (DNA) synthesis and mitotic activity in individual cells. Megaloblastic anemia is the latest stage of folate deficiency, and it may not present until the third trimester; however, white cell morphologic and biochemical changes signaling deficiency may precede overt anemia. In experimental animals maternal folate deficiency is associated with an increased incidence of congenital malformations. Malformations can also occur in infants of women using folate antagonist drugs such as the anticonvulsant medications phenytoin (dilantin), carbamazepine, and dtphenylhydantoin. Oral contraceptives and some antibiotics (trimethoprim, triamterene, and carbamazepine) may also cause folate insufficiency. Approximately 2500 new cases of NTDs occur in the United States each year Moreover, NTDs have a fairly high recurrence rate in future pregnancies (i.e., approximately 2% to 10%).
Red blood cell (RBC) folate concentrations exceeding 906 mmol/L (400 ng/rnl) are associated with the fewest NTDs. In a study of 189 healthy women attempting to become pregnant, only one in four women had RBC folate levels greater than 90 mmol/L. Women who consumed only food sources of folate had the lowest folate intake and the lowest RBC folate concentrations. Only those women who consumed folic acid supplements in addition to dietary folate achieved RBC folate concentrations considered to be optimal for protection against NTDs.
The Centers for Disease Control and Prevention (CDC) have recommended that all women of childbearing age increase their intake of folic acid because 50% of all U.S. pregnancies are unplanned and the neural tube closes by 28 days of gestation (before most women realize they are pregnant). Therefore supplementati( m with folic acid should begin before conception—hence the CDC’s general recommendation to increase folate intake throughout the child-bearing years. The Food and Drug Administration (FDA) has mandated that grain produces such as bread, rice, and pasta be enriched with folic acid. women of childbearing age should be encouraged to take a folic acid supplement and to include generous amount of folic acid food sources in their diets.
Women who smoke, consume moderate-to-heavy alcohol, or use recreational drugs are at risk for marginal folate status, as are those using oral contraceptives, anti-seizure medications (such as phenytoin), and those with malabsorption syndromes. Women using anti-seizure medications must be closely monitored when start ng folic acid because folic acid supplementation can reduce seizure threshold.
Fewer than 40% of US. women are taking folic acid supplements periconceptually as evidenced from a telephone survey through the California Teratogen Information Service between 2003 and 2004. Three hundred twenty seven women were called to assess attitudes and compliance toward advice to continue vitamin use following pregnancy to be protected in a future pregnancy.
Not all countries have a folate food fortification program in place. Currently only the United States, Canada, and Chile have programs and have documented the reduction of NTDs by 31% to 78%.
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