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In 1991, a randomized trial funded by the Medical Research Council demonstrated that folic acid supplementation before pregnancy and during its early stages markedly reduced the risk of neural-tube defects in newborns.1 This finding — which indicated that neural-tube defects may be considered to represent a vitamin-deficiency disorder — led to the recommendation that all women who are planning to become pregnant should take folic acid supplements beginning before pregnancy is recognized and continuing through its early stages. Once a pregnancy has been confirmed, it is probably too late for supplemental folic acid to be protective.In this issue of . . .
Nicholas Wald (Wed,) studied this question.