By John Gever, Senior Editor, MedPage Today

Published: October 12, 2011

The percentage of teens 15 to 19 years old reporting that they have had sexual intercourse has continued a long-term decline and now stands at just over 40%, according to CDC survey data from 2006 to 2010.

Notably, the long-standing gender gap in adolescent sexual experience appears to have vanished, thanks to an especially steep decline in the proportion of boys and young men who reported having lost their virginity.

When a similar survey was conducted in 1988, 51.1% of unmarried teen girls/women and 60.4% of teen boys/men said they had had sexual intercourse at some point. In 2006-2010, these figures fell to 42.6% of women and 41.8% of men.

At the same time, among those who reported having sex, the proportion who used condoms during their first encounter has risen to 80% among males and 60% among females, the CDC reported. In the 1988 survey, barely half of either sex reported condom use at first sex.

The findings came from the agency's National Survey of Family Growth (NSFG), which the agency has conducted periodically since 1988. In the most recent round, the survey involved 4,662 teens 15 to 19 years old, split about evenly between the sexes. Previous versions of the survey were given in 2002, 1995, and 1988.

For some sexual behaviors that adults typically try to encourage in teens, the numbers suggested that progress has been made:

Contraception use at first sex: 68.9% of women and 71.4% of men in 1988; 78.3% of women and 85.4% of men in 2006-2010
Contraception use at last sex: 79.9% of women and 84.2% of men in 1988; 85.6% of women and 92.5% of men in 2006-2010
Used condom 100% of the time in past four weeks: 41.4% of women and 88.2% of men in 1988; 49.0% of women and 88.5% of men in 2006-2010

Perhaps less encouraging, young women had become more likely to report a history of multiple sex partners.

Among sexually experienced, unmarried teen women, 43.6% said in 1988 that they had had three or more partners in their lifetimes. In the 2006-2010 survey, the number increased to 48.6%.

The increase was seen both among respondents saying they had had three to five partners and among those reporting six or more.

Adolescent men, on the other hand, were more likely to report having three to five partners (32.6% versus 28.6% in 1988) but less likely to say they had had six or more (22.4% versus 26.7% in 1988).

Also, compared with 1988, young women in the most recent survey were more likely to report that their first sex was with a new acquaintance, "just a friend," or occasional dating partner, and less likely to have been with a steady boyfriend.

The opposite was true for young men.

Still, there remained a large gap between sexes in the nature of relationships at first sex: 56% of boys/men versus 70% of girls/women said their first encounter was with a steady dating partner. Nearly twice as many adolescent men as women said their first sex was with a new acquaintance or "just friends" (28% versus 16%).

For the first time in the 2006-2010 edition, the NSFG asked adolescents about the "wantedness" of their first sexual encounters.

Some 11% of the females and 5% of males indicated that they "didn't really want it to happen at the time," whereas 41% of the teen women and 63% of the men were eager for it.

A middle option, "mixed feelings," was selected by 48% of the girls/women and 33% of boys/men.