The pills you have to worry most about missing are the ones right before and right after the seven placebo pills in your pack. Known as the pill-free interval, the placebos are designed to be taken the week you have your period to help you stay in the rhythm of taking a pill every day. If you start a new pack late or take longer than seven days "pill free," you might ovulate and could become pregnant. Read the package insert that came with your pills; it will explain what to do about missed pills. Or call your health care professional. In the meantime, use backup contraception just to be safe. In general, if you miss a pill, take it as soon as you remember and then continue taking one pill each day as prescribed (depending on when you missed your pill, you may take two pills on the same day). If you miss two or more pills in the first week of your pill cycle and you have unprotected intercourse during this week, consider using emergency contraception. If you miss pills in the fourth week of a 28-day pack, those pills are likely placebo if you're using a 21/7 regimen. However, some of the newer formulations may contain active pills, so read the package insert for instructions.