Most teenagers are horrified at the very idea of discussing sexual matters with their parents. Equally, some parents are too embarrassed to bring it up, instead leaving informative books on the bedside table, or simply hoping their children will pick up the basics by osmosis.
Increasingly, however, in a world of social media and readily-available porn, it's more important than ever to discuss issues such as consent, self respect and protection, from both STIs and pregnancy, with teenagers.
One person who seemingly has no problem doing so is Gwyneth Paltrow, who revealed this week that she tells her own children, Moses, 15 and Apple 17, whom she co-parents with ex-husband Chris Martin:
"You have to stay really close to your own truth and you have to stay in integrity with that truth... I always encourage my children to listen to their integrity and .. what feels right."
But more cringe-induceingly, she also revealed on The Ellen DeGeneres Show this week that Moses is 'proud' of her for selling vibrators through her Goop store, even though she admitted he's 'uncomfortable' just seeing a bra strap.
"Can I tell you the sweetest thing?" Gwyneth went on - no doubt embarrassingly for her strapping teen son. "A few months ago he said, 'You know, Mom' — out of nowhere — 'I was really embarrassed for a minute that Goop sold vibrators.'
"'And then I realised, no, this is great. You're making people feel not embarrassed to buy something, and that's great. You're a feminist.'"
Gwyneth then admitted that Moses was probably still embarrassed. Even the coolest stars find their teens are mortified by them, as Zoe Ball discovered on Celebrity Gogglebox this summer with Woody, her 18 year old son.
Watching Netflix's Too Hot to Handle, Zoe asked her son about men's masturbation habits.
"Do you have to empty them every... I'm a girl, I don't know," she said, to Woody's horror. "What if you don't empty them and you're being surrounded by girls like that. How painful would that be?"
"Some people don't need to do it," her horrified son muttered. "There's monks and stuff, they're celibate. I just... I don't want to have this conversation with you!"
Not surprisingly, most teens don't. But at some point, most parents are going have to deliver some advice on the topic of sex. So how do you minimise the horror for all involved?
Tanith Carey, author of What's My Teenager Thinking?, written with child clinical psychologist Dr Angharad Rudkin, advises, "you should be certainly asking where your child thinks babies come from by the age of about six.
Read more: How to talk to children about sex
"That’s because by this developmental stage, children are more curious about their place in the world and where they came from," she explains. "If they don’t get the facts, they use a process called ‘magical thinking” which means they make up a story to explain what they don’t yet understand."
As time goes on, she adds, "the key is to keep talking. As your child gets older, let the topic come up naturally again so you can add more context, such as how sex is something nice for adults who love each other.
"In Gwyneth’s case, some parents may believe that she’s given her teen son Moses TOO much detail," Carey adds.
"But I am impressed that a 15-year-old boy is already thinking about female pleasure because he's heard his mother discuss it. Boys tend to get a very one-sided, male orientated view of sex from viewing pornography – and mums have traditionally left it to fathers to talk about sex with their sons.
"However, the fact that teenage girls are reporting feeling uncomfortable with some of the acts they are asked to do - which are copied from porn – means in my view it's a good thing that Gywneth is discussing the female perspective with him.
"Though teens usually seek to keep their sex lives private, as a parent, we should remember that parents always remain our children's important source of information," adds Carey.
"While it may feel awkward at first, being brave and honest with your teen can help head off future issues, such as an unplanned pregnancy or sexually transmitted infection, which can affect their future health and fertility.
"Again if you are not sure where to start, offer to answer questions whenever they have them.
"Don’t just focus on the physical side of sex either, but talk about the link between intimacy and emotions and mutual pleasure," she says.
"This way your teen is likely to make better choices for themselves."
Younger teens will probably be embarrassed at first , says Jo Mitchelhill, a qualified teacher, foster career, and Parenting Coach.
Jo advises, "I was always honest about sex. If they asked questions about it, then I would answer them as honestly as possible in an age-appropriate way."
Her tips for successful talking are:
1 The best time to have a conversation about sex is when you are out walking or driving in the car with your kids. That way you are having a conversation where you aren’t eye balling them, and they can ask questions without having to see your face.
2 Make sure you have spoken to your partner (if relevant) and you know what they are comfortable with you sharing. Remember your kids are always going to want to think that you have never had sex and they don’t want to even imagine that you know what it is. So normalise it in conversation.
3 Talk about sex in the same way that you would talk about shaving or washing yourself. It is something that most of us do and it is important to keep ourselves safe at all times. If we normalise the conversation, it is less embarrassing for everyone involved.
4 If you are worried because it embarrasses you, find a friend who you can have the conversation with and practice using the words without being embarrassed. If we are embarrassed then our kids will be as well. Penis, vagina and semen are just words like, arm, leg and blood. There is nothing naughty or dirty about them.
Watch: How to talk about sex with your LGBTQIA child