No sex please, we're your parents. Would you let your teen have sex under your roof?Getty

Your 15-year-old daughter glances up from Facebook. "Hey Mum, is it okay if Fred stays over tonight when we come back from the party? His parents can't pick him up, and taxis are so expensive."

Stay over. It sounds simple. But you don't have a sofa bed and there is no spare room, so it's not simple.

Part of your head is screaming, "Noooooooo!" but keen to be uber cool you hear yourself say brightly, "Where do you think he'll sleep?"

"In my room, of course!"

And there is your dilemma. What do you do when your teenage son or daughter wants to share their room - and possibly their bed - with the latest girlfriend or boyfriend?

It's a dilemma that has the coolest parents scratching their heads, not knowing what is right. They might not be having sex, but on the other hand they might be. Some parents - and I include myself here - break out in a cold sweat thinking about enthusiastic teenage sex and the thin walls of your average house- especially when it's a son or daughter on the other side of the wall.

It throws up so many questions. Even if your teens are clued-up about contraception, are you right to allow underage sex in your home? What if, heaven forbid, the girlfriend became pregnant under your roof and you had to face her parents' reaction? And if your teens are over 16 there is still the question of whether this is a long term relationship, or not much more than a one-night stand. Should you appear to be condoning this?

Although teenagers vary in their emotional maturity, there is still some pressure and expectation to be sexually active. But as parents we know that being in a sexual relationship involves emotions – and how do these mix with the pressures of GCSEs and A levels? Should we turn a blind eye - knowing it may well happen anyway - or enthusiastically provide bed and breakfast?

Michelle, whose son is just 18, knows exactly what she thinks. "If Ryan wanted a girl to stay over, I would allow it as long as they had been seeing each other for at least six months. I would also want to be sure that her parents were happy with the arrangement. I would not allow it if it was a casual relationship. If he asked if a girl could stay, I would assume they were having sex."

But what if he had asked when he was only 16? "I would have had an in-depth chat with him about sex and relationships, and told him that legally he was still a child."

At the same time though, Michelle admits that there is not a lot parents can do if their sons or daughters are intent on having sex, and may do so wherever they can, but adds, "It's more about what I feel comfortable with in my home."

This view was reiterated by Sophie, who explained, "It would depend on how I felt about the boy, and if I thought my daughter had a good understanding of contraception. But I think her father would be against it, so sleeping on the sofa would be the most likely option."

Which is what Jo agreed to when her 15-year-old daughter asked if her boyfriend could stay over after a party. "I said he could have the futon downstairs. It looked slept in the next morning, but as I was asleep when they came in, who knows what happened."

Kathy, whose two sons are now late teens had ground rules. "I always said they could not have casual over-nighters. If they were in a serious relationship, we were happy to allow girls to stay as long as they disappeared before breakfast. I just didn't want to meet girls on the landing in the morning; it was too in-your-face."

The overriding opinion from the mums I talked to was: it's your home, so you set the rules according to what you feel comfortable with.

And keep communicating - talk to your teen about your concerns and see if you can find a compromise which keeps everyone happy.

Do you let girlfriends and boyfriends stay over?
What's your reasoning on whether to let them or not?