In study prepared by the FDA regarding the effectiveness of birth control it was found that:
For Combined Pill (Estrogen/Progestin) user, the percentage of women whom sometimes forgot to take a birth control pill as directed and became pregnant, or birth control pill was used correctly but failed anyway is 5% and for women whom always took a birth control pill as directed but still became pregnant is 0.1%.
For users of the minipill (Progestin only) the percentage is 5% for women whom sometimes forgot to take a birth control pill as directed and became pregnant, or birth control pill was used correctly but failed anyway and 0.5% for women whom always took a birth control pill as directed but still became pregnant.
For depo-provera users, the percentage of women whom sometimes forgot to take a birth control pill as directed and became pregnant, or birth control pill was used correctly but failed anyway is 0.3% and 0.3% for women whom always took a birth control pill as directed but still became pregnant.
For Norplant users, the percentage of women whom sometimes forgot to take a birth control pill as directed and became pregnant, or birth control pill was used correctly but failed anyway is 0.09% and 0.09% for women whom always took a birth control pill as directed but still became pregnant.
To view the study click ----->here