Why are morning after pills more effective when taken as soon as possible? To answer this, we need to delve a little bit into how hormonal emergency contraception works.
Morning after pills help prevent pregnancy by delaying ovulation, i.e. the release of an egg. Once released, the egg is viable for 12-24 hours, after which it will dissolve. Sperm can live inside the body for up to five days, so delaying the egg release means they will have nothing to fertilise and will die off before ovulation occurs. ellaOne® has also been found to be effective at delaying ovulation right before ovulation was due to occur.
The morning after pill only works by delaying ovulation. It cannot interrupt an existing pregnancy, prevent implantation or cause an abortion. If you have already ovulated, the morning after pill won’t be effective.
The exact timing of ovulation is really hard to predict. Even though we have apps and information available to help us track our menstrual cycles, what happens within that cycle can still vary from month to month and from person to person.
You may not ovulate at the exact same time every month, and various factors like stress, changes in sleeping patterns and diet can affect when you ovulate as well. This means that it’s still a good idea to take hormonal emergency contraception as soon as possible after unprotected sex, so you have a better chance of taking it before ovulation occurs.