Living wills represent the chance for patients to declare their wishes in advance of situations in which they become no longer competent to do so. They are revocable by the patient at any time and are automatically invalid if the patient is pregnant, as another being is involved. Living wills can be set aside if a long period has elapsed since their drafting and the wishes are not known to be current. Also, there is the potential for conflict if the patient has signed a donor card and prolongation of life would be needed to carry out those wishes. Generally, such action would not be honored unless relatively expeditious arrangements were possible.