At a general meeting of the LDS Relief Society, the First Presidency and Twelve issue the "Proclamation on the Family" including the statement: "We further declare that God has commanded that the sacred powers of procreation are to be employed only between man and woman, lawfully wedded as husband and wife." It concludes: "We call upon responsible citizens and officers of government everywhere to promote those measures designed to maintain and strengthen the family as the fundamental unit of society." Aside from this statement's usefulness in LDS campaign against the legalization of same-sex marriages in Hawaii, the hierarchy's repeated emphasis on the importance of its being a "proclamation" suggests that this announcement will one day be presented for the sustaining vote of the general conference and added as a numbered document in the Doctrine and Covenants. However, the change in the wording of President Packer's 2010 conference talk, where the proclamation was origianlly called a 'revelation' but was changed to a 'guide' might indicate that canonization isn't inevitable.
[The Mormon Hierarchy - Extensions of Power by D. Michael Quinn, [New Mormon History database (http://bit.ly/NMHdatabase)]]