I'm not sure that can be correct... The packaging says that you don't need back up protection during your period. They wouldn't put that in there if it wasn't true -- they'd have so many lawsuits, birth control pills would hardly be on the market. I know they can't prevent pregnancies 100%, but they can protect you during your period even though you're not taking the pills. I just wanted to know how they do that. Just to clarify, I always use back up even though I take the pill religiously. I simply wanted to know how it works.