According to school nurses, increasing numbers of teenagers are taking part in a group sex activity known as "daisy-chaining", but experts are wary of believing it is widespread.
Young people often exaggerate details of their sex lives
Described by nurses as "having sex in a similar way as swinging", the term "daisy-chain" comes from the gay community, says Dr Gary Wood, of the University of Birmingham.
He said it was hard to gauge how common the act was among young people as there were no statistics.
"Sometimes these stories get pushed out of all proportion," he cautioned.
However, he said the prospect of engaging in something deemed unsuitable could be tempting for young people.
"People tend to explore sex. There are lots of images in the media and in advertising about sex, but it's still repressed, it's still forbidden.
"As something that is seen to be in need of regulation, it is seen as more dangerous to young people."
At the Royal College of Nursing conference in London this week, Judy McRae, a sexual health nurse in London, said: "Colleagues are coming across reports of groups of young people having sex in large groups.
"It is known as daisy-chaining and is obviously very worrying as far as sexually transmitted infections and pregnancy is concerned.
"As we understand it, it involves groups of older teenagers going round to each other's homes and having sex in a similar way as swinging.
"It is very new and is only just starting to be talked about."
Dr Wood recently took part in sexual health workshops in Birmingham with about 500 young people aged 14 to 16 - and the concept of "daisy-chaining" did not arise.
"But the questions they asked left nothing to the imagination," he said, adding that "nothing surprises" him about sex.
"For most teenagers, the first they would know of 'daisy-chaining' would be when they read it in the papers."
The group sex nature of the activity would raise questions of sexuality for males, Dr Wood said.
"Young men are frightened of being labelled gay. One of the strongest elements of peer pressure for boys is not being labelled as gay," Dr Wood said.
However, the issue of sex among teenagers did highlight the need for nurses to be trained in giving sexual health advice.
Talking the talk
Jan Barlow, the chief executive for young persons sexual health charity Brook, said: "It's also essential that every young person has comprehensive sex and relationships education in schools, which not only teaches them how to protect themselves but also gives them opportunities to discuss issues such as how to resist peer pressure to take part in unwanted sexual activity."
Spokeswoman Catherine Evans said that, while she was not aware how common "daisy-chaining" was, young people often felt that "everyone else" was having sex.
"This is usually not the case - we know that the majority of young people don't become active until late in their teens."
She added that there was a "tendency among young people to talk about sex more than they are actually doing it".