Teenagers watching television are bombarded with nearly twice as many sex scenes as seven years ago, according to a new study by the Kaiser Family Foundation.

Sex, lots of sex. Sex, sex, sex. Casual sex, dirty sex. Hot, sweaty, recreational sex with desperate housewives on expensive, carved, imported-from-Italy dining tables. Adolescent girls performing oral sex on middle-aged managers of expensive clothing stores in backrooms jammed with nekkid mannequins in exchange for some of that expensive clothing -- plus accessories!

In the slightly more than 1,000 shows scrutinized in the study, nearly 4,000 scenes had sexual content, compared with fewer than 2,000 in 1998, when the foundation started studying TV sex.

And yet the rate of teen pregnancy in this country has plunged by about one-third during approximately the same time.

Clearly, the television networks are doing something wrong.

Especially since, of the TV programs pregnant with sexual content (70 percent of all shows, averaging about five sex scenes per hour), only a very small percentage included a message about the risks and responsibilities of sex.

Only about 14 percent discussed contraception, abstinence or other "safe sex" messages, the study found, though Kaiser veep Vicky Rideout, who oversaw the study, admitted during its unveiling yesterday that a first good-night kiss at the door between two television characters probably does not call for an on-screen discussion between the guy and chick as to whether they should use a condom.

Yes, the Kaiser study includes a first good-night kiss at the door in its definition of "sexual behavior." And "sexual content" includes any discussion about sex.

Given that, it's a wonder they found only 4,000 scenes in those 1,000 shows over the course of the study. Maybe they didn't get some of the jokes in those "Sex and the City" reruns on TNT.

TNT is, in fact, among the networks scrutinized for the study, along with HBO, Lifetime and USA cable networks, though why they chose those particular networks over ones that, say, teens actually were watching, like MTV, remains a mystery to The TV Column.

Last year, for instance, 6 percent of HBO's viewers were teens, compared with nearly 30 percent ages 50 and older. Lifetime, the Men Are Pigs and the Women Who Love Them network, had an audience of only 4 percent teens and more than half age 50 and older. More than 40 percent of the audience for USA Network and TNT was 50 or older and about 5 percent were teens. MTV had nearly 30 percent teens in its audience, 3 percent viewers 50-plus.

But, as with most studies, it's best not to ponder these things too closely lest the top of one's head start to come off. Back to the study:

ABC, CBS, NBC, Fox and WB shows also were included, though not UPN. Again, out of consideration for the top of our head, we'll think about that tomorrow.

"Given how high the stakes are, the messages TV sends teens about sex are important," Rideout said in the news release handed out yesterday and, in slightly different form, live to those attending the unveiling of the study at the Kaiser Family Foundation digs at 13th and G (which, by the way -- very plush).

Why, we wondered, given that, despite TV's best effort, teen pregnancy rates had plunged, fewer teens are having sex and more of those who are having intercourse are using protection.

University of Arizona at Tucson communications professor Dale Kunkel, who worked on the study, noted sourly that just because there has been a decline doesn't mean that all groups are working toward that end. He said he worries that the media are working against groups trying to remedy the problem.

He's comforted, no doubt, by the fact that teen pregnancy numbers are still higher in this country than elsewhere.

That's even though many of those countries with lower teen pregnancy rates don't regulate TV content nearly as much, noted Tony Vinciquerra, president and CEO of Fox Network Group, who, along with Kunkel, was part of a panel discussion during the unveiling ceremony. Also participating were FCC Commissioner Kathleen Abernathy, "Law & Order: SVU" executive producer Neal Baer, National Campaign to Prevent Teen Pregnancy Executive Director Sarah Brown and Rand Corp. behavioral scientist Rebecca Collins.

Vinciquerra noted that his Fox Reality cable network can't rerun much reality programming from overseas because it's too risque for this market. Based on our observations yesterday, Vinciquerra has risen to great heights at Fox because of his almost superhuman ability to attend the Mad Hatter's tea party and not grab the Dormouse by the shoulders and shake it until its teeth rattle when it suggests that things are just different in this country because television has become our religion, in a way. The Dormouse in this case being FCC Commissioner Abernathy.

There was nobody on the panel to speak up for the 65 percent of the country's homes in which no one under 18 resides and some of whose favorite TV shows were under discussion, and not in a good way. Very little discussion also about the fact that nearly 70 percent of kids have TVs in their bedrooms, bought for them by parents -- 83 percent of whom, the Kaiser foundation says, firmly believe that exposure to sex on TV contributed to children becoming involved in sexual situations before they're ready.

Sen. Barack Obama, fresh from his brilliant overshadowing of Jon Stewart on Comedy Central's "Daily Show" earlier in the week, continued his "I'm So Over-Hyped" tour with an appearance at the debut of the "Sex on TV" study, addressing a conference room packed with what appeared to be a handful of reporters, some lobbyists from networks monitoring the situation and -- judging by the knicker-knottedness of the questions directed to the Illinois Democrat after his speech -- members of TV watchdog and other special-interest groups.

Obama killed. Yes, he quoted Newton Minow's famous "vast wasteland" speech. Politicians always do. But he had some other material. Like how, when he watches TV with his young daughters and they're in the middle of a family program and a commercial for Cialis comes on, "It's more than troubling to find yourself wondering how you'll explain certain medical conditions that last longer than three hours to a 4-year-old and a 7-year-old."

Not terribly original, but good stuff. More talk about how the adult content on "Schindler's List" is good while the adult content on "Desperate Housewives" is "far different." And "we don't teach our children that healthy relationships involve drunken naked parties in a hot tub with strangers -- but that's what they see when they turn on 'The Real World.' " Undeniable facts, all.

"What do we do when bad television becomes the enemy of good parenting?" Obama asked. We steeled ourselves for the worst.

"I think, as parents, we have an obligation to our children to turn off the TV," he suggested.

Revolutionary!

Company for dinner: Eva Longoria and Jesse Metcalfe on "Desperate Housewives."