Nutrient Folic Acid May Help Prevent Spinal Cord Birth Defects

Women who take multiple vitamins containing folic acid during the first six weeks of pregnancy are much less likely to have babies with spinal column defects like spina bifida than women who do not, a study suggests.

The occurrence of such defects among babies of women who took such vitamins was 0.9 per 1,000, according to a three-year study of 22,776 women by Dr. Aubrey Milunsky of the Center for Human Genetics at the Boston University School of Medicine and colleagues.

That compared to a defect rate of 3.3 per 1,000 among infants born to women who did not use supplements, the researchers reported in today’s Journal of the American Medical Assn.

“We believe that the combined data from this and other studies provide good evidence that folic acid-containing multivitamins taken during the first six weeks of pregnancy will prevent, by more than 50%, the occurrence” of such defects, they wrote.

The results also indicate that the preventive effect “is limited to use in the first six weeks of pregnancy,” the researchers said.

Most pregnant women see their doctors for the first time 8 to 10 weeks after conception, Milunsky said in a telephone interview Wednesday.

“Almost all the fetal organs have been formed at that time. An opportunity for useful intervention would have been lost,” he said.

The function of folic acid--found naturally in liver, leafy green vegetables, mushrooms and lima and kidney beans--is not really known, Milunsky said.

It is “probably instrumental in the chemistry of the cell, allowing cells to migrate and move and close the spinal cord. That happens in the first six weeks,” he said.

Among the cases studied, 49 babies were born with spinal column, or neural tube, defects.

These included spina bifida, in which incomplete closure of the bony casing around the spinal cord typically leads to mild or severe paralysis, and anencephaly, in which major parts of the brain are lacking and death usually occurs within hours.

Researchers noted a “strikingly higher” prevalence of the defects--13 per 1,000--among infants of women with a family history of spinal conditions who did not take supplements, compared to women with such histories who did take supplements--3.5 per 1,000.

“Our finding is consistent with the idea that a genetic predisposition interacts with an essential nutrient deficiency, possibly a deficiency of folic acid,” they wrote.

The researchers noted that studies have not ruled out the possibility that vitamins A, C, D or E--alone or with folic acid--protect against the defects, because all were contained in most of the multivitamins.

They also cautioned that excessive doses of multivitamins could be harmful.