British Columbia's teens are waiting longer to have sex for their first time, but experts are warning that "sexting" and the rise of diseases related to oral sex still put them at risk.

The McCreary Centre Society, a Vancouver-based non-profit that does research on youth health, has released the results of its fifth provincewide survey of more than 29,000 public-school students from Grade 7 through Grade 12. The 2013 data showed 75 per cent of those asked reported never having intercourse or oral sex.

That is up from 72 per cent in the 2008 survey and 70 per cent in 1992. The new survey didn't ask the teens why they were waiting. But when the 2008 survey asked the question, half cited waiting to meet the right person or not being ready and almost 40 per cent said they didn't want to be involved in a pregnancy.

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Annie Smith, McCreary's executive director, said the latest survey asked separate questions about oral sex because public health nurses across the province were increasingly reporting sexually transmitted infections such as herpes around students' faces.

"A lot of them were not seeing it as sex and therefore a lot of them were not taking any precautions," Ms. Smith said.

Of those who had had oral sex, only 17 per cent had used a barrier such as a condom or a dental dam.

Ms. Smith said 2013 was also the first year the survey asked teens specifically about "sexting" – sending explicit photos or messages over phone – and 9 per cent reported engaging in such activity.

"Sexting is a concern, because young people are putting information about themselves out there that they then can't take back and in some occasions it's being used against them for bullying purposes," Ms. Smith said.

Alex McKay, one of Canada's foremost experts on sexual health, said it was "highly encouraging" that 90 per cent of the sexually active teens in the survey reported using either a condom, birth control or both contraceptive methods the last time they had sex.

"Yet on the other side of the coin, about almost a third didn't use a condom and thereby put themselves at risk for an STI," Dr. McKay said from Toronto, where he is executive director of the Sex Information and Education Council of Canada charity.

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Sexually active teens are increasingly in favour of switching condoms for birth control pills after the age of 17, which mirrors what Dr. McKay and other researchers have found in studies of Canadian university students, the demographic that consistently shows the highest rate of STIs.

He added that many young Canadians aren't aware of the high prevalence of STIs among their peers and likely don't understand that the "vast majority of cases of STIs have no symptoms and that the partners who can potentially give them STIs don't know that they're infected."

As well, Mr. McKay and SIECCAN's latest data on teen pregnancy found B.C.'s rate of 29.5 per 1,000 teens was just slightly above the national average in 2010 and had declined at a rate below most other provinces in the previous decade.

He said the McCreary Centre's data shows a maturity in waiting to have sex and mirrors trends from government studies in the United States. But he said the data can't be compared with the rest of Canada because B.C. is unique in funding provincewide research on the issue.

That research gives provincial governments a "big payoff" not only in terms of identifying problems with sexual health and STIs but also in targeting those problems to save the health-care system from the "hefty annual bill" related to serving those patients, Dr. McKay said.

"STIs are a fairly significant burden on the health-care system," Dr. McKay said.

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Kristen Gilbert, a sex educator and director at Planned Parenthood B.C., said a generation of B.C. children have grown up learning more about sex-ed than their counterparts in Ontario, where teaching kindergarten students the names of sexual organs is still controversial.

"When you were a kid you probably learned 'Head and shoulders, knees and toes,' but really, that song is 'head and shoulders, don't talk about, don't talk about it, knees and toes,'" Ms. Gilbert joked.

"There's a whole area of the body that we don't even have names for and people have the right to know what their body parts are named and how they function."