All the birth control methods do not provide 100% protection against becoming pregnant. Failure rates depends on the methods of contrception used. The highest failure rates is in practicing rhythm method. Lowest failure rates are seen in combined oral pills and norplants.

Failure rates of contraceptive methods in first 12 months of use

Methods	Pregnancy rate per 100 women years
No method	80%
Rhythm	24%
Coitus interruptus	19%
Male condoms	14%
Diaphragm	20%
IUCD	0.5-2%
Combined oral pills	0.1%
Progestin only pill	1%
DMPA and NET injectables	0.3%
Norplant	0.1%
Vasectomy	0.15%
Tubectomy	0.5%
Lactational amenorrhea	2%