If you miss a day of birth control, what happens depends on how many pills you have missed and where you are in your pill pack. Generally, if you miss one pill, you should take it as soon as you remember and then take the next pill at your regular time. If you miss two or more pills, you may need to use backup contraception, such as condoms, for the next seven days. If you miss three or more days or it has been longer than 48 hours since you took a pill, you are no longer protected against pregnancy, and you should consider emergency contraception if youve had unprotected sex in the last five days or if the pills were missed during the first week of the pack. The two biggest side effects of missing birth control pills are breakthrough bleeding and pregnancy.