N.M. Stat. § 59A-22-33
An individual or group hospital or medical expense insurance policy delivered or issued for delivery in this state that provides that coverage of a dependent child of an insured, or of an employee or other member of the covered group, shall terminate upon attainment of the limiting age for dependent children specified in the policy shall also provide, in substance, that attainment of the limiting age shall not operate to terminate the coverage of a child while the child is, and continues to be both incapable of self-sustaining employment, by reason of intellectual or developmental disability or physical disability, and chiefly dependent upon the policyholder for support and maintenance. However, proof of the incapacity and dependency of the child must be furnished to the insurer by the insured employee or member within thirty-one days of the child's attainment of the limiting age and subsequently, as may be required by the insurer, but not more frequently than annually after the two-year period following the child's attainment of the limiting age.
NMS § 59A-22-33