Mo. Rev. Stat. § 469.100: Special rule for persons attaining majority — transfers after 1976.

In the case of a transfer made after 1976 creating an interest or future interest that has vested in a person before such person's twenty-first birthday, such interest shall be subject to disclaimer as provided in this chapter until nine months after the person's twenty-first birthday. No act or conduct of the person prior to such twenty-first birthday, other than a written acceptance, shall constitute an acceptance of any portion of the interest.