§ Mr. David Atkinsonasked the Secretary of State for Education and Science what assessment he makes of the statistical significance of the difference in recurrence rates of neural tube defect between supplemented and unsupplemented mothers was due to vitamin supplementation.
§ Mr. WaldenI understand that the difference in the recurrence rates of neural tube defects between supplemented and unsupplemented mothers was statistically significant, that it to say, it was unlikely to have been chance alone. However, while the statistical significance of the results is not in question the medical significance is. There are two possible explanations for the difference, namely, that the vitamins reduced the risk of neural tube defects or that the women who took supplements were in any case at a very low risk of having neural tube defect pregnancies and therefore were not comparable with the women who did not.
The Medical Research Council and its advisers believe that, on present evidence, it is not possible to judge which of these explanations is the right one and that the way to find out is to conduct a properly controlled clinical trial. The trial is therefore proceeding, although it is too soon to draw any conclusions.