Two IUDs contain 52 mg (20 mcg a day for 5 years, 10 mcg a day after 5 years) were originally used for 5 years with a cumulative 5-year pregnancy rate of 0.5 to 1.1%; additional studies report them to be effective at 7 years with a cumulative 7-year pregnancy rate of 0.5 to 1.1%.