Which do teens do first: oral sex or sexual intercourse? Do teens use oral sex to delay first intercourse?

New CDC data put numbers on how many young Americans in their teens and early 20s have oral sex with opposite-sex partners -- and when they do it. The numbers come from 6,346 in-depth, computer-assisted interviews with 15- to 24-year-olds conducted from July 2007 to June 2010 as part of the National Survey of Family Growth.

The numbers show that young teens vary widely in their heterosexual behavior.

Some teens do appear to have oral sex to put off or at least delay first intercourse:

    Among females ages 15 to 19, 7.1% report oral sex but no vaginal intercourse, and 15.8% report having oral sex before first vaginal intercourse. In this age group, 45.8% said they'd never had sex of any kind.
    Among females ages 20 to 24, 3.1% report oral sex but no vaginal intercourse, and 36.2% report oral sex before first vaginal intercourse. In this age group, 9.9% said they'd never had sex of any kind.
    Among males ages 15 to 19, 10.3% report oral sex but no vaginal intercourse, and 15.4% report having oral sex before first vaginal intercourse. In this age group, 44.2% said they'd never had sex of any kind.
    Among males ages 20 to 24, 2.8% report oral sex but no vaginal intercourse, and 31.7% report oral sex before first vaginal intercourse. In this age group, 13% said they'd never had sex of any kind.

Young females who were youngest at age of first intercourse were more likely to have had vaginal intercourse before having oral sex. Young women with factors linked to later age of first vaginal intercourse -- mothers with a college or higher education and two parents living at home -- were more likely to report oral sex but not vaginal intercourse.

Yet data from an NIH study suggest that young people who put off vaginal intercourse by having oral sex don't wait very long for full sexual initiation.

The CDC study also finds that:

    About two-thirds of males and females ages 15 to 24 have ever had oral sex, and the same percentage has had intercourse.
    Among males ages 15-24, 24% had first oral sex before first vaginal intercourse, 24% had oral sex after first intercourse, and 12% had first oral sex on the same occasion as first intercourse. 6.5% had oral sex but not vaginal intercourse.
    Among females ages 15-24, 26% had first oral sex before first vaginal intercourse, 27% had oral sex after first intercourse, and 7.4% had first oral sex on the same occasion as first intercourse. 5.1% had oral sex but not vaginal intercourse.
    A higher percentage of boys ages 15 to 19 reported receiving oral sex (47%) than giving it (35%). For girls the same age, about the same percentage gave as received oral sex (41% and 43%).
    Non-Hispanic black males ages 15 to 24 were less likely than non-Hispanic white or Hispanic males to have given oral sex to an opposite-sex partner.
    Non-Hispanic black females ages 15 to 24 had the highest percentage of ever having had vaginal intercourse (74%), followed by Hispanic females (68%) and non-Hispanic white females (66%).
    Non-Hispanic white females reported ever having had oral sex more often (69%) than did non-Hispanic black females (63%) or Hispanic females (59%).

The CDC report is published online by the National Center for Health Statistics.