Hormonal birth control methods like the pill, patch and ring, as well as condoms, are primary contraceptives, or ‘plan A’. It’s when these fail for some reason that emergency contraception, also known as the morning after pill or plan B, may need to be considered.
An example might be a condom falling off during sex, or if you forget to take your pill and then have unprotected sex. Contraception emergency is given in the form of a one-off pill, and needs to be taken within a certain time period after unprotected sex to protect against pregnancy (normally 72 or 120 hours, [popover id=ref2] depending on what you use).
The morning after pill works in a similar way in the body to hormonal birth control, but the two are not interchangeable. Plan A can’t be used in the place of plan B, and vice versa.
If you’re worried that you may be pregnant because your primary contraceptive method has failed, see a clinician right away as the emergency contraceptive pill might not be suitable.