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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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