Regarding Use Of Folic Acid Before Planning A Pregnancy

A 25-year-old woman presents for preconception counseling. She wants to know more about nutrition, particularly about folic acid. She has read a lot about it in magazines. You can tell her that:

A. Folic acid supplementation is associated with an increased level of alpha-fetoprotein in maternal serum.
B. She needs to take either a prenatal vitamin or a supplement that provides at least 4 mg (4,000 µg) of folic acid.
C. She needs to start folic acid supplementation as soon as her pregnancy test is positive.
D. Most women get enough folic acid through their diet.
E. Folic acid requirements are higher in women with type 1 diabetes mellitus.

Answer And Discussion:

E. Folic acid requirements are higher in women with type 1 diabetes mellitus.

Women with insulin-dependent diabetes are at significantly higher risk of neural tube defects (NTDs) and require 4 mg daily supplementation. Folic acid has been proven to reduce the risk of NTDs. On a maternal serum panel, elevated alpha-fetoprotein levels are associated with open NTDs; therefore, folic acid is associated with normal levels. 

Folic acid requirements for all women who may become pregnant are 400 µg. The only patients who need 4 mg are women who are at high risk for fetal NTDs, such as those who have given birth to an infant with an NTD previously, those on anticonvulsants, and those with type 1 diabetes mellitus. Since the neural tube closes 4 weeks after fertilization, the need for folic acid is greatest prior to the first missed menses. Waiting until the pregnancy test is positive is too late. 

More than two-thirds of women do not get enough folic acid in their diet. Folic acid has been proven to prevent 50% or more of neural tube defects, which include anencephaly and spinal bifida. The other half of NTDs are multifactorial or genetic. One month prior to conception and through the first trimester, women should avoid folic acid antagonists such as aminopterin, pyrimethamine, trimethoprim, triamterane, sulfasalazine, methotrexate, and anticonvulsants (e.g., valproic acid and carbamazepine).