For birth control pills, why are you protected when taking placebo pills but not if you miss regular pills?

Question

I think I need this explained from the beginning because l’m missing something. You are protected during the placebo pills even though those pills don’t do anything, right? So technically you can skip the week of placebo pills and be just fine – meaning you are not taking birth control for a week and are still protected. But why do people get pregnant if they miss regular pills? Help me make sense of this.

Disclaimer: Yes, I understand there’s always the possibility of getting pregnant even if you use birth control pills correctly.

In: Biology

Answer 1

OCPs create an interval of infertility. They do so by inducing anovulation(ovum is not released) and making the uterus unfavorable to implantation. This effect is required surrounding the day of ovulation which is usually day 14 in a 28 day cycle. The purpose of placebos in an OCP regiment is to cause endometrial shedding or menstruation. They do so by removing the hormonal stimulant needed for endometrial growth. Implantation cannot take place during this period.