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The causation of neural tube defects – a journey of discovery and the challenge of prevention
For centuries the causation of neural tube defects remained unknown. Neural tube defects are serious birth defects that occur worldwide, in some places as frequently as 1 in every 200 births. About half of cases are spina bifida, and most of the remainder are anencephaly, with or without spina bifida. Anencephaly is fatal within a few days of birth and spina bifida usually results in severe physical disability. In 1991, in the MRC vitamin study, it was shown that lack of a B vitamin, folic acid, was an important cause of these defects. The study showed that folic acid supplementation could prevent about three-quarters of neural tube defects. This result led to governments recommending that women who may become pregnant take a folic acid supplement before pregnancy. It also led to over 70 countries mandating the fortification of flour with folic acid to help overcome the fact that many women overlook taking supplements before pregnancy. The preferred fortification level should be to provide an additional 0.4 mg a day of folic acid to the population and the preferred supplement dose for women who may become pregnant is 4 mg or 5 mg a day, as there is evidence that the higher dose confers additional protection. Many countries, including the UK, have failed to introduce mandatory fortification and as a result children have been born with serious birth defects that could have been prevented. This represents a governmental failure. It is like having a polio vaccine and not using it in countries in which paralytic polio occurs.