Nutritional supplementation and prevention of congenital abnormalities.

Recent intervention studies have shown a reduction of occurrence and recurrence of neural tube defects caused by the periconceptional supplementation of folic-acid-containing multivitamins or pharmacological doses of folic acid alone. This new primary preventive method can also reduce the occurrence of other major congenital abnormalities, mainly the reduction of conotruncal cardiovascular malformations, defects of the urinary tract, congenital hypertrophic pyloric stenosis and congenital limb deficiencies. The rate of cleft lip, palate, or both, was not lowered by periconceptional multivitamin supplementation, however. The underlying biologic mechanisms of this protective effect are not still understood, but naturally occurring folates (polyglutamates) or synthetic folic acid (monoglutamate) have a key role. The debate over supplementation concerns which vitamins (folic-acid-containing multivitamins, or folic acid alone); what doses (0.4 mg, 0.8 mg or 4 mg folic acid) and to whom (whether it is worthwhile differentiating between women at high and low risk). At present there are three possibilities: folate- and other vitamin-rich diet, supplementation, and food fortification to provide appropriate multivitamin and folic acid consumption for all women of childbearing age who are capable of becoming pregnant.