How effective is ulipristal acetate if taken on the day of ovulation? I had relationship with a guy and he was wearing a condom. However, i was in doubt that some may have slipped so i took ulipristal acetate few hours later. I checked an ovulation calculator and it says my ovulation is may 1st, when i had sex. First day of my last period was april 15 and march 15 was prior to that. Will the pill still work? Help pls. Thank you