The study authors wrote that it is not known how B12 and folate might interact to influence the formation of the neural tube, the embryonic structure that gives rise to the spine and brain. They noted that the two vitamins are jointly involved with several key biochemical reactions, as well as with the synthesis of DNA. Lack of either Vitamin B12 or folate in any of these chemical processes theoretically could increase the risk of a neural tube defect.
The authors noted that their results needed to be confirmed by other studies among other populations of women. They suggested, however, that women should have Vitamin B12 levels above 300 ng/L before becoming pregnant. (Because B12 levels drop sharply during pregnancy, the researchers adjusted the levels measured during pregnancy to provide a target level for women to achieve before they become pregnant.)
Because Vitamin B12 comes from foods of animal origin, women who adhere to a strict vegan diet may be at risk for a B12 deficiency, said an NICHD author of the paper, James L. Mills, M.D., senior investigator in the Division of Epidemiology, Statistics, and Prevention Research. He added it is advisable for women with digestive disorders that interfere with the absorption of foods to consult a physician before getting pregnant, to make sure they are receiving adequate amounts of B12.
Dr. Mills explained that critical events in the formation of the brain and spinal column occur very early in pregnancyin the first 28 days after conceptionbefore many women even realize they are pregnant.
He added that the U.S. Public Health Service recommends that all women of childbearing age consume 400 micrograms of folic acid each day. This amount assures that a woman will have adequate stores of the vitamin, in the event of an unintended pregnancy.
"If women wait until they realize that they are pregnant before
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NIH/National Institute of Child Health and Human Development