Maternal Folic-Acid Levels--Possible Link to Down's Syndrome.

In a preliminary study funded by the Food and Drug Administration (FDA) Office of Women's Health, the National Center for Toxicological Research (NCTR) has identified biochemical and genetic evidence of impaired folate metabolism in mothers of children with Down's syndrome. A leading cause of mental retardation, Down's syndrome occurs in one out of every 700 live births. Results from the study have been published in the American Journal of Clinical Nutrition.

According to Commissioner of Food and Drugs Jane E. Henney, M.D., the study "lends support to FDA's March 1996 decision to require the fortification of certain grain products with folic acid."

Beginning in January 1998, FDA mandated the addition of 140 micrograms of folic acid, a B vitamin, to every 100 grams of certain grain products, such as flour, breakfast cereals, and pasta. This decision, based on evidence that inadequate folate status in early pregnancy increases the risk of neural-tube defects, was intended to reduce the incidence of birth defects in the brain and spinal cord.

Down's syndrome, or trisomy 21, is a complex genetic disease caused by an extra copy of chromosome 21. In most cases, the extra chromosome results from an error in maternal chromosome separation before conception. The results of the new study, led by S. Jill James, Ph.D., a biochemist at NCTR, indicate that mothers of children with Down's syndrome have an imbalance in folate metabolism. The imbalance may be explained, in part, by a common genetic variation in an enzyme involved in the folic-acid pathway.

It is important to note that while the NCTR study may provide new insight, larger clinical studies will be necessary to confirm its findings and to determine definitively whether folic-acid supplementation, beginning at least two months before pregnancy, will reduce the incidence of Down's syndrome.