There is no way to prevent this condition. Genetic counseling is useful for affected people and their families.
Infertility is the most obvious long-term effect of Klinefelter syndrome. Many affected individuals, however, develop diabetes or thyroid disease. Life span is usually normal.
Klinefelter syndrome is not contagious. Since males with Klinefelter syndrome are usually infertile, there is little risk they will pass the disorder on to children.