Preventing Down Syndrome?

Is Down syndrome just a random event that more commonly strikes the children of older mothers? Is there nothing that can be done to prevent it except getting pregnant at a younger age or detecting and rejecting the affected child?

A study in the September 1999 American Journal of Clinical Nutrition suggests that Down syndrome is linked to an inadequate supply of folic acid, a B vitamin. Mothers who have a hereditary tendency to lower folate levels have a much higher risk of having a child with Down syndrome. Up to 320% higher! Taking folic acid supplements before conception is proven to prevent several birth defects, including spina bifida and other neural tube defects. It may well be that this simple measure can also dramatically reduce the risk of Down syndrome.