I-pill is to be taken as soon as possible after sex .Sooner you take the pill more effective it will be.
If taken within first 12 hours of unprotected sex they prevent pregnancy
95-99% of cases.
If taken after 12 hours but before 72 hours after intercourse, emergency contraception
pills prevent pregnancy about 75-89% of the time.
It does not work if a fertilized egg has already implanted in uterus