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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.
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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.
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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.
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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.
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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.
Results published in New England Journal of Medicine
1999;341:1509.
Related work by CDC staff
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Berry RJ, Li Z, Erickson JD,
Li S, Moore CA, Wang H, Mulinare J, Zhao P, Wong LY, Gindler J, Hong SX,
Correa A. Prevention of neural tube defects with folic acid in China
(China-U.S. Collaborative Project for Neural Tube Defects), New England
Journal of Medicine 1999;341:1485-90. [Abstract]
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Honein MA, Paulozzi LJ, Mathews TJ, Erickson JD,
Wong LC. Impact of folic acid fortification of the US food supply on the
occurrence of neural tube defects. Journal of American Medical
Association 2001;285:2981-2986. [Abstract]
Date: June 17, 2005
Content source: National Center on Birth Defects and Developmental
Disabilities
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