Q I’ve always been open with my 15-year-old daughter about sex; I was young when I had her and we are more like sisters. She has started asking questions about “what I got up to” with boys when I was her age. I had an uninhibited sex life, and although I have no regrets, I wouldn’t necessarily recommend it to anyone else, so I’m having to be evasive for once. Can I answer her honestly?

A It’s the eternal parental dilemma, isn’t it? “How can we teach our teenage children to have a healthy attitude to sex but prevent them from actually having any?” So many parents worry that if they talk about sex with their kids, they endorse or encourage it, but let’s face it, sex is the world’s worst-kept secret. Whether a parent chooses to discuss the subject or not, his or her child will find out about it, and eventually engage in sexual activity anyway.

Sexual guidance doesn’t boil down to a single conversation, and having been open with your daughter means that the blueprint for her future sexual behaviour is already in place. Years of questioning, discussion, negotiation and, indeed, your own example, mean that your daughter already has a pretty clear idea of your moral stance on the subject, so you should not be concerned that her opinion of you will change if you are honest about your early experiences.

As long as you make it clear that you want her to interpret what you are saying as a caution rather than a licence, sharing the trials and tribulations of your early relationships can be an effective way of encouraging an open dialogue about sex.

Whether it is admitting to mistakes you made, or describing the excitement of your first crush, talking about your early forays into the world of love and sex provides a rare opportunity for you to put yourself on the same level as her, and it also puts paid to the typically teenage view that parents know nothing about sex.

When my kids found a diary I kept when I was a teenager, all was revealed; they were particularly fascinated by one rather elusive early boyfriend who came out of the closet decades later. At the time I found it embarrassing, especially the bit where my mum made me go on the Pill, but, retrospectively, I think it was helpful for them to see how goofy and unsure of myself I had been back then. And of course, it was all safely in the past tense.

While teenagers can handle the concept of a cuter, younger version of their parent having sex, the idea of wrinkly, saggy, ageing adults engaging in any form of physical intimacy is unthinkable.

You describe your youth as “uninhibited”, but the chances are that you were also a lot less well-informed than your daughter. In that context, the fact that you have “no regrets” is largely due to good luck and, needless to say, there are more reliable ways of ensuring that your daughter can feel positive about her early sexual experiences. Nor do you say whether her conception was unplanned.

If it was, it is possible that her specific interest in your early sexual behaviour is an attempt to establish the impact her arrival had on your life. This obviously makes your task slightly more difficult. How do you steer a course between reassuring her that she was wanted, while impressing on her that having a child when you are very young can make life more complicated?

Tony Kerridge, a spokesman for Marie Stopes International, a leading provider of sexual and reproductive healthcare services, suggests that you “outline your aspirations for her and tell her that you want her to reach her full potential before she considers having a child”. He also says that “although it is aimed primarily at teenagers, parents and teachers say that they find the straightforward tone of the organisation’s Like It Is (www.likeitis.org ) website useful as a prep before difficult conversations. I would also recommend Everything You Never Wanted Your Kids to Know About Sex But Were Afraid They’d Ask, by Justin Richardson and Mark A Schuster (Amazon, £7.61). Good luck.

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