Contraception, or birth control, is a broad term referring to any method people use to avoid becoming pregnant. In this lesson, you will learn about the five main categories of contraception: natural, chemical, barrier, hormonal, and the intrauterine device. Each category will be discussed in more detail later in the lesson.

Effectiveness Regarding contraception, effectiveness refers to how well the contraceptive method prevents pregnancy. To compare the effectiveness of different methods of contraception, it is helpful to understand how scientists measure it. First, it’s important to distinguish between actual and theoretical effectiveness.

Theoretical effectiveness is how well the contraceptive method would prevent pregnancy over the course of a one year if it were used exactly as intended.

Actual effectiveness is how well the method prevents pregnancy in actual couples who use it over the course of one year. In real life, unexpected things happen: for example, people sometimes forget to refill prescriptions, and condoms sometimes break. Looking at the statistics on actual effectiveness will give you a much better picture of how reliable a form of contraception is.

Second, it is helpful to compare the effectiveness of a contraceptive to the statistics on conception. For example, unprotected sex—sexual intercourse without contraception of any kind—has a contraceptive effectiveness of 15%. What does that mean? It means that only 15% of couples having unprotected sex for one year will avoid getting pregnant. In other words, over the course of one year, 85 out of 100 couples having unprotected sex will become pregnant. (100 – 15 = 85)