Effective contraceptive use generally requires planning and preparation prior to having sexual intercourse. This is often a problem for adolescents because young people usually report that their first sexual intercourse "just happened" and that they were not planning to have sex at the time. Consequently, condoms, which require the least amount of advance planning, are used more than any other method of contraception at first sexual intercourse, but about 35 percent of first intercourse experiences take place without the use of any contraception at all.
Avoiding pregnancy after the first (often unplanned) sexual intercourse experience requires consistent use of an effective contraceptive method. This can be additionally problematic for adolescents because young adolescents tend to be less deliberative and rational about sexual decisions than older persons, and they also tend to have sexual intercourse more sporadically. Consequently, approximately one-fifth of adolescents report that they did not use any effective contraceptive at their last intercourse experience. Seven in ten pregnancies to adolescent teens occur to teens who were not using any method of contraception when they became pregnant.
A major challenge to preventing pregnancies is the fact that so many adolescents delay seeking contraceptive services until some months after they have become sexually active. The delay between first intercourse and obtaining contraceptive services has been found to average almost one year in some studies. Procrastination, not thinking that they could get pregnant or being ambivalent about sex, contraception and pregnancy, and worrying about confidentiality are the reasons sexually active adolescents most often give for not seeking contraceptive services sooner. The year after the initiation of sexual intercourse is a time of high risk for unintended pregnancy, and in one study about one-third of adolescents made their first visit to a clinic because they suspected that they already were pregnant. Thus, helping adolescents to plan for effective contraception (preferably before, but at least soon after initiating sex) could be an important strategy for reducing unintended pregnancy.
There are developmental patterns such that the older adolescents are when they first have intercourse, the more likely they are to use contraception. Stronger preferences to avoid pregnancy and higher educational aspirations and achievement are related to earlier and more consistent contraceptive use. Over time, sexually active adolescents, especially those in longer-term couple relationships, increasingly use the pill.