Proportions of unintended pregnancy rates attributable to imperfect adherence, by method3 14
| Contraceptive method | Probability of failure, typical use | Probability of failure, perfect use | Proportion of UP rate attributable to imperfect adherence |
|---|---|---|---|
| OC | 0.0900 | 0.0030 | 0.967 |
| Ring | 0.0900 | 0.0030 | 0.967 |
| Patch | 0.0900 | 0.0030 | 0.967 |
| Injection | 0.0600 | 0.0020 | 0.967 |
| Implant | 0.0005 | 0.0005 | 0.000 |
| IUD | 0.0080 | 0.0060 | 0.250 |
| IUS | 0.0020 | 0.0020 | 0.000 |
| Barrier methods* | 0.1800 | 0.0200 | 0.889 |
| Withdrawal | 0.2200 | 0.0400 | 0.818 |
| Calendar method† | 0.2400 | 0.0400† | 0.792 |
| No method (chance) | 0.4600 | 0.4600 | NA |
*Data for male condom used as a proxy for barrier methods.
†Ovulation method used as a proxy for calendar methods.
IUD, intrauterine device; IUS, intrauterine system; NA, not applicable; OC, oral contraceptive; UP, unintended pregnancy.