"i took this pill for the first time about 48 hrs after an accident.  the lady at the counter told me thats how she had 2 of her kids.  well, she was right because i ended up pregnant.  fast fwd 3 yrs, within a two month time span the condom came off twice. took the pill within hrs and got my period. next time took it also within hours and got my period a week and a half early and it was very heavy and lasted almost 2 weeks. so my experience is if you take it right away you are probably fine. if not, your luck goes down with each passing hour. oh also the last time i took the generic form. that was the fist time i had such heavy bleeding from it. next time i may stick w brand name. if needed"