The Act of Succession of 27 March 1953 is an act adopted after a 1953 referendum in Denmark and dictates the rules governing the succession to the Danish throne. The 1953 referendum changed the act so that it became possible for a woman to inherit the throne if she has no brothers, a system known as male-preference cognatic preference primogeniture. As the reigning King Frederik IX had three daughters and no sons, this made Princess Margrethe heiress presumptive to the throne, replacing her uncle Prince Knud. As Frederik IX's wife Queen Ingrid was not expected to have any more children, this effectively ensured that Princess Margrethe would become Queen of Denmark, which she did in 1972. The act also removed the succession rights of minor members of the House of Glücksburg.