How well does the progestin only pill (POP) work?
Progestin-only pills have a theoretic contraceptive effectiveness of 90 to 99 percent. The failure rate is lowest in highly motivated women. The effectiveness drops off dramatically with missed or delayed pill administration. The Pearl index is 0.3-4/100 women years (failure rate for 100 women using the method for one year).The higher Pearl index results when adherence is poor, particularly in very young users. The lower rate applies particularly during lactation.
