IRREGULAR PERIOD

MY WIFE TOOK THE SHOT, ONE WEEK BEFORE HER PERIOD. AND NOW ITS 1 WEEK AFTER HER DUE PERIOD AND NOTHING YET?? IS THIS NORMAL?
CAN I TRUST THIS SHOT FOR ME TO NOT USE ANY OTHER PROTECTION, AND KNOW SHE WILL NOT GET PREGNANT?
Posted by CHINO; updated 08/12/05