lˈɑːɹdʒ stˈʌdiz əkɹˌɑːs θˈaʊzəndz ʌv mˈɛnstɹuːəl sˈaɪkəlz hæv fˈaʊnd ɪt təbi ɪfˈɛktɪv ɪn pɹɪvˈɛntɪŋ pɹˈɛɡnənsi.
Large studies across thousands of menstrual cycles have found it to be effective in preventing pregnancy.