What do the sugar pills in birth control do?

The sugar pills basically don't have any hormones such as progestin and ethinyl estradiol which allows you to have your period. The sugar pills are normally taken on the 4th week of your Birth Control cycle. You don't need to take the sugar pills as guided because either way you will have a period with or without talking the sugar pills on the 4th week. The sugar pills also keeps you on a schedule when on a birth control pill since many do not take them responsibly which may result in an unplanned pregnancy.

You can also skip the sugar pills and go right into your next pack of active pills and just have no periods. Read Malcolm Gladwell's "John Rock's Error" and that is what seasonale and lybrel are (skipping placebos)