Does the length of the placebo pill week affect hormonal birth control efficacy?

Yes. the 1 week placebo was originally established with much higher dose pills specifically 100mcg of estrogen component and now we are at 35 mcg and 20mcg. So, we have seen escape ovulation at day 6 or 7 of placebo in some patients. Thus, to be safer, you could consider decreasing the placebo week to just 4 days or 5 days.

In fact, I suggest skipping the placebo week altogether. There is no need for that week. Read John Rock’s Error