4. A declarant may execute an advance directive for health care at any time. The advance directive shall be signed and dated by, or at the direction of, the declarant in the presence of two subscribing adult witnesses, who shall attest that the declarant is of sound mind and free of duress and undue influence. A designated health care representative shall not act as a witness to the execution of an advance directive. Alternatively, the advance directive shall be signed and dated by, or at the direction of, the declarant and be acknowledged by the declarant before a notary public, attorney at law, or other person authorized to administer oaths. An advance directive may be supplemented by a video or audio tape recording. A female declarant may include in an advance directive executed by her, information as to what effect the advance directive shall have if she is pregnant.