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Neural tube defects: a two-pronged approach to primary prevention.

It is generally agreed that neural tube defects (NTD) have a multifactorial etiology when genetic factors render the developing fetus susceptible to intrauterine environmental factors acting during the fourth week of gestation to interfere with the orderly closure of the neural tube.1 As there is little likelihood that anything can be done about the genetic background, primary prevention would therefore be dependent on eliminating these factors from the environment or avoiding them. My intention here is to enlarge on some aspects of primary prevention of NTD as outlined by Smithells in an earlier issue (Pediatrics 69:498, 1982).2 One environmental factor, poor maternal nutrition and, more particularly, folic acid deficiency seems now to have been identified, but there are almost certainly a number of others.