Parents alarmed by a new national study showing more than half of teens ages 15 to 19 have engaged in oral sex — but unsure how to broach the topic with their own sons or daughters — may turn to a new book for "The Real Truth About Teens & Sex."

The book by Sabrina Weill, former editor-in-chief of Seventeen magazine, achieves the balanced approach suggested by the book's subtitle, "From Hooking Up to Friends with Benefits — What Teens are Thinking, Doing and Talking About and How to Help Them Make Smart Choices."

While some opt for oral sex to avoid virginity loss or pregnancy, many teens view it as less intimate than intercourse and consider it a "base" (usually third), Weill writes. The percentage of teens who have engaged in oral sex rises to nearly seven of 10 by age 18-19, according to the National Center for Health Statistics study.

Weill, who conducted her own survey for her book, found nearly half of 12- to 17-year-olds consider someone who does "everything but" sexual intercourse a virgin. Another quarter "don't know."

"It's interesting that nearly a quarter of teenagers seem unsure about what qualifies as virginity loss — this used to be a rather cut-and-dried issue. It speaks to new and shifting boundaries and new ways of talking and thinking about sex that this is no longer the case."

While she believes few teens participate in the more hyped examples of oral-sex parties (sometimes known as rainbow or chicken parties), parents need to be realistic about statistics: There's at least a 50-50 chance teens are having either intercourse or oral sex or both.

In one study, researchers asked parents if their teens were having sex. Parents who said yes were correct nearly every time. But less than half of those who said no were right.

Weill obviously respects and likes teens. She includes their voices so the book is grounded in their real and varied experiences. It isn't a grown-up expert spouting off on what kids do these days.

While asserting that many teens lack "the maturity, judgment or sophistication to make possibly life-changing decisions regarding sex," she falls on the better-informed-is-better-prepared side.

She doesn't claim to stop teens from sex but notes that "all experts and scientific evidence point to this solid fact: When parents ... connect with and communicate clearly with teens about sex and sexuality, the teens make smarter, more responsible choices."

And parents do have an impact, often more than they think. Almost half of parents guessed friends held the most sway on their child's decisions about sex, but less than a third of teens said the same thing. Instead, nearly half of teens cited parents as the most influential, according to a 2004 National Campaign to Prevent Teen Pregnancy study.

Some of her tips:

• Don't wait for teens to initiate the conversation. "You can always ask me" is a cop-out since teens are often reluctant to do so without an opener, Weill notes.

• Talk to teens one-on-one about sex and dating. Otherwise, teens can feel like they're being ganged-up-on. Ask what "sex" means to them; their answer might be different than what you expect.

• Turn the tables. Many girls say they fear losing a boyfriend if they don't have sex. Telling a teen, "He's not worth it if he won't wait," isn't enough because she probably doesn't agree. "Instead, talk about what she is worth, and ask her to turn the tables. Would she dump her boyfriend if he didn't want to do something that she was ready to do?"

• Emphasize that sex shouldn't "just happen." Unplanned sexual experiences, especially involving alcohol, are often unprotected, leading to a higher risk of pregnancy and sexually transmitted diseases. Girls often don't like to "plan" to have sex since this isn't considered romantic.

• Use statistics to get into the topic. Parents can mention that seven of 10 teens believe most students their age have had sex, but only half of teens actually have. Or note that eight of 10 sexually active young teens (age 12 to 14) say they wish they'd waited longer.

• Talk about love rather than sex. When parents really listen — rather than dismiss teens' strong feelings as infatuation — they may find teens have many relationship questions.

• Be aware of Big Events. Be clear with teens that it's not OK for someone to expect sex just because of a special occasion, be it prom, graduation, New Year's Eve or an anniversary.

• Don't extract a confession. "Making a teen feel like he can't talk about sex without being judged or attacked will make it far less likely that he'll ever bring up the topic again, even when he really needs help or advice."