Abnormal folate metabolism in mothers with Down syndrome offspring: review of the literature.

Altered maternal folate status and homozygous mutation in the methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) genes can promote chromosomal instability and non-dysjunction resulting in fetal trisomy 21. Folate supplementation around conception therefore has the potential to reduce the frequency of Down syndrome. This finding, in addition to the prevention of neural tube defects, strengthens the recommendation to use folic acid around conception.