[Risk related to methodologically disputable studies: the example of vitamin therapy for the prevention of neural tube defects].

Due to the non acceptance by ethics committees of its double blind controlled study for prevention of neural-tube defects recurrence by vitamin supplementation versus mineral components, a British group underwent methodologically debatable epidemiological study which has become quite controversial. This survey concluded that vitaminotherapy is effective. The aim of this article was to analyze the consequences induced by such a procedure which probably resulted in delaying the onset of the Medical Research Council controlled trial, performed with the necessary rigorous methodology, and which gave the final answer only 11 years later, a time during which concerned women could not take advantage of a valuable preventive treatment.