If you’ve already ovulated, EllaOne will not work. Nor will any other form of emergency contraception either. It’s very hard to predict when you’re going to ovulate since your cycle can change from month to month. The best thing to do is take EllaOne as soon as possible after you have unprotected sex, to reduce the risk of ovulating during that time.
Emergency contraception works by preventing ovulation, so in the case that an egg has already been fertilised, EllaOne won’t have any effect and it won’t cause an abortion.