How emergency contraceptive pills work

Emergency contraceptive pills work by inhibiting or delaying ovulation.1,2 

They work to prevent pregnancy after unprotected sex by quickly postposing ovulation, if it has not already happened. This means that the sperm waiting in the fallopian tubes will be unable to meet an egg and fertilise it. This is similar to regular contraceptive pills, which also work by preventing egg release.

Emergency contraceptive pills are not 100% effective.1 This is because there is a chance that you may have already ovulated when you take an emergency contraceptive pill. Taking emergency contraceptive pills as soon as possible after unprotected sex gives the best chance of success.3

The sooner you take emergency contraceptive pills, the better·

  • Emergency contraceptive pills are not 100% effective.1·
  • ellaOne® is the only morning after pill that is still effective when risk of pregnancy is highest1,4,5·
  • The sooner you take emergency contraception, the better the chance of successfully postponing ovulation and avoiding pregnancy.3


Emergency contraceptive pills will not protect you from pregnancy if you have further unprotected sex.3

woman holding a condom

If you want to have sex after using an emergency contraceptive pill, use a barrier method of contraception until your next period.