Excerpt from the full fact sheet:

Emergency contraception (EC) is safe, effective, and simple to use.  It is not associated with any serious or harmful side effects, and it is not dangerous for women with particular medical conditions.  In addition, women can diagnose their own need for treatment.   For these reasons, EC meets the FDA's criteria for over-the-counter drug status. However, for more than three years, the FDA denied approval on the application to make EC an over-the-counter drug, thus blocking many women's access to a safe and effective means of preventing pregnancy. Finally, in August 2006, the FDA approved non-prescription sales for EC but only for women ages 18 and older.

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