Legal Definitions - fertile-octogenarian rule

The fertile-octogenarian rule is a legal concept that used to be applied to the rule against perpetuities. This rule stated that a person is capable of having children no matter their age or physical condition. The rule against perpetuities requires that the owners of property in a will be ascertainable within a certain period of time. If a person having a child would break the rule against perpetuities, the person will be considered capable of having a child no matter their age or physical condition.

For example, if a person creates a trust that will last for 100 years after their death, the rule against perpetuities requires that all beneficiaries of the trust be ascertainable within 100 years. If the trust includes a provision that gives the property to the first child of the grantor's great-grandchild, the fertile-octogenarian rule would allow the great-grandchild to have a child at any age, even if they are over 80 years old.

Most states have changed this rule by limiting the age of fertility considered for the rule, or instead of considering what could possibly occur, some states wait and see what actually occurs to see if the rule is broken.