Each year spina bifida and anencephaly, the two most common forms of neural tube defects, occur in approximately 1 of every 1,000 pregnancies in the United States and in an estimated 300,000 newborns worldwide. Only recently have researchers made some progress in preventing these defects. The results of randomized trials now indicates that at least half the cases of neural tube defects could be prevented if women consumed sufficient amounts of the B vitamin folic acid before conception and during early pregnancy.  

• The development and closure of the neural tube is normally completed within 28 days after conception, before many women are aware that they are pregnant.  It is generally accepted that neural tube defects are caused by the failure of the neural tube to close. The embryologic basis of the clinical variation in neural tube defects is poorly understood. The genetic controls of the cellular mechanisms of closure have yet to be determined,  although several possible associated genes have been identified in animal models.

• The incidence of spina bifida and anencephaly varies considerably worldwide. For example, the incidence of these conditions in North China is six times greater than their incidence in South China.  

• Unfortunately, the full potential of folic acid to prevent neural tube defects has not been realized, despite some fortification of cereal products with folic acid in the United States and despite recommendations by various health agencies that women who could become pregnant consume 400 micrograms of folic acid daily. Every day, preventable disabilities continue to occur.  Every day, fetuses and infants are affected who otherwise would be born without these serious anomalies. 

• The urgent challenge facing medical and public health professionals with respect to neural tube defects is how to translate our knowledge about primary prevention into practice. In the United States, options for prevention include increasing the level of fortification of grains, increasing the consumption of foods now fortified with folic acid, and increasing the consumption of vitamin supplements containing folic acid. Improving the knowledge and changing the habits of women and medical professionals will be critical in efforts to realize the full preventive potential of folic acid. The global health community must make a concerted effort to meet the challenge.