The labeling mandated by the U.S. Food and Drug Administration (FDA) for Plan B and Ella state that they may interfere with implantation, but according to a June 2012, The New York Times article, many scientists believe that they work only by interfering with ovulation and are arguing to have the implantation language removed from product labels.
美国食品和药物管理局（FDA）对Plan B和Ella规定的标签表明它们可能会干扰植入，但根据2012年6月的“纽约时报”文章，许多科学家认为它们仅通过干扰排卵来起作用并且正在争论从产品标签中删除植入语言。