An Overview of Failure Rates for Birth Control
Accidental pregnancy can occur with any form of birth control (other than with abstinence). This is known as birth control failure. Obviously, birth control failure is most likely to occur if the method of birth control is not used correctly or consistently. However, accidental pregnancy can occur even with perfect use of birth control. That being said, some methods of birth control do have higher failure rates than others.
Perfect Versus Typical Birth Control Failure Rates
Often, if applicable, birth control rates are calculated both for "perfect" use and for "typical" use. The data for perfect use comes from couples who used their method of birth control correctly and consistently.
The data for typical use, however, presents a more realistic picture, as it includes couples who did not use their method correctly and consistently. This may not seem "fair" to include couples who did not use the method perfectly; however, it does provide important information regarding which methods are more difficult for couples to use reliably.
Barrier and/or Spermicide Methods
Barrier and spermicide methods of birth control are notoriously prone to failure. They have very high failure rates, compared to most other methods. See the following table for information on failure rates for barrier and spermicide birth control: