There is very little build-up in your system(24-48 hrs), that's why if you miss a pill or more than one pill the supression of your hormones on your ovaries is diminished and can release an egg making you susceptible to pregnancy. There is no protection during the 7 week sugar/reminder pill week for your menses/period. The pills are only helpful in preventing pregnancy, and are not foolproof even if taken daily as evidence of a pregnancy of mine, one for my sister-in-law resulting in my niece, and countless others; and also does not protect against anything else, such as STD's, safe sex, not always so safe without additional protection.