Sexual activity and pregnancy are rare among 10–12-year-olds, and when sexual activity occurs at such early ages, it is frequently nonconsensual.[1] According to an analysis of data from the 2006–2010 National Survey of Family Growth (NSFG), about 1% of 12-year-old females have had sex; this proportion is in contrast to 19% of 15-year-olds and 32% of 16-year-olds. In general, these proportions are slightly higher among males than females. Moreover, more than half of females who have had sex by age 10 or 11 say the sex was not voluntary; the proportion decreases as age at first sex increases. The pregnancy rate for 2008 ranged from about one per 1,000 among 13-year-olds to 62 per 1,000 among 17-year-olds.

In the context of “a broad public perception that a substantial proportion of young adolescents are sexually active,” the researchers sought to provide updated estimates of sexual activity, contraceptive use and pregnancy rates among U.S. adolescents, including those aged 12 and younger. To examine the timing of first heterosexual vaginal intercourse, event history analyses were performed with data from the 1984–1993 birth cohorts of the 2006–2010 round of the NSFG, a nationally representative survey of men and women aged 15–44. The proportion of individuals who had had sex at each age and the proportions reporting nonconsensual first sex were calculated. Birth cohorts from 1939 to 1991 from the 1988, 1995, 2002 and 2006–2010 rounds of the NSFG were used to examine trends in age at first sex over time. The researchers calculated the proportion reporting contraceptive use at first sex and the interval of time between first sex and first contraceptive use by age at first sex. National data on births and abortions were used in conjunction with census data to calculate pregnancy, birth and abortion rates for 2008 by age at outcome.

Overall, fewer than 1% of 10-year-olds, 1% of 11-year-olds and 2% of 12-year-olds have had sex. The proportions were slightly higher for males than for females. For example, 1% of 12-year-old females have had sex, compared with 4% of 12-year-old males. The level of sexual experience increases with age—19% of 15-year-old and 32% of 16-year-old females have had sex. By age 20, 76–77% of males and females have had sex.

Among females who had sex by their 10th birthday, 62% said that their first sex was nonconsensual. The proportion decreased as age at first sex increased: Fifty percent of those who had sex by age 11 reported nonconsensual first sex, compared with 23% of those who had sex by age 12 and 5–7% of those who had sex by ages 13–17.

Trend data revealed that at no time in the past 50 years has the proportion of female adolescents who had sex by age 14 ever been 10% or greater. Among all of the birth cohorts examined, the median age at first sex was never below age 17, and at least 25% of adolescents had not had sex by age 19. Adolescents in the most recent cohorts were less likely than those born in the 1970s to have had sex by any given age.

Adolescents who had sex early were less likely to have used a contraceptive method at first sex and took longer to initiate contraceptive use than those who had sex later. For example, 52% of females who initiated sex at age 12 or younger used a contraceptive at first sex, compared with 82% of those who were aged 16 at first sex. One year after first sex, three-quarters of those who were 12 or younger at first sex reported contraceptive use, compared with nearly all of those who were 16 at first sex. The pattern of contraceptive initiation among those aged 14 or younger at first sex was significantly different from that among those aged 19 at first sex; however, the pattern among those aged 15 at sexual initiation was not.

Pregnancy at ages 12 and younger is very rare: Among all 12-year-olds, about one in 7,000 get pregnant in any given year. For 2008, the pregnancy rate was one per 1,000 among 13-year-olds and five per 1,000 among 14-year-olds, and ranged from 16 to 62 per 1,000 among 15–17-year-olds. The majority of pregnancies among females aged 13 and younger end in abortion, but at older ages, the reverse is true. For example, at ages 13 and younger, the number of births is 69% of the number of abortions; at ages 17 and older, twice as many pregnancies end in birth as in abortion.

The researchers acknowledge several study limitations: Reports on dates of first sex and first contraceptive use may be subject to social desirability bias, nonconsensual first sex may have been underreported, sexual activity was limited to heterosexual vaginal intercourse, and the measures of sexual activity and contraceptive use are based only on the first occurrence of each. The researchers note that their findings indicate that “concerns about substantial levels of sexual activity among young adolescents are unfounded.” They suggest that health professionals screen all patients for unwanted sexual activity, “with the awareness that sexual activity among the youngest adolescents is especially likely to be nonconsensual.”—L. Melhado

Reference

1. Finer LB and Philbin JM, Sexual initiation, contraceptive use and pregnancy among young adolescents, Pediatrics, 2013, doi:10.1542/peds.2012.3495, accessed Apr. 26, 2013.