II.

Effectiveness

No birth control method, other than abstinence from sex, is 100 percent effective in preventing pregnancy. Some methods are more effective than others, and scientists use two types of pregnancy rates when describing effectiveness. Method effectiveness, or perfect use, is the percentage of pregnancies that occur when a particular method is used correctly and consistently with each act of sexual intercourse. User effectiveness, or typical use, is the percentage of pregnancies that result from average use of the method, which accounts for improper or inconsistent use. This article provides typical use statistics in its overview of birth control methods.