Ask your teen about their friends
Ask what your child's friends think about the subject. This can be a way of talking about your child's thoughts and fears indirectly. For example, if you see a pregnant woman, you could say, "When I was a teenager we were scared of getting pregnant. Do your friends ever worry about that?"
Talk about sex little and often
Don't have one big talk about sex. Make it an open, ongoing topic. Have lots of little talks whenever the subject comes up, and start before your child is a teenager. Let your teen know that they can talk to you about anything that's on their mind.
One of the easiest ways to bring up the topic is during everyday activities like washing up or watching TV. This makes it less of an event. You can use the storyline in a program, or a celebrity in the news. For example, you could say, "What do you think about the fact they've had sex?"
Find out what they're learning about sex at school
Ask your teenager's school what they are teaching your child about sex and relationships. Ask your child what they think about this. Find out if there's anything they don't understand, and if their classes have raised any topics they'd like to discuss with you. You could say, "What do you think of the sex and relationships lessons you're getting at school?"
Listen to what your teen thinks about sex
Ask your teenager how they feel about things, for example, waiting to have sex with someone they care about. You could say to them, "Do you think it's worth waiting until you meet someone you really care about, and who cares about you, before you have sex?"
If your teen may be gay, lesbian or bisexual
Your child might be gay, lesbian or bisexual. If so, they still need to know about safer sex messages, including how to protect themselves against STIs and pregnancy. They might use a discussion about sex and relationships as an opportunity to come out (tell you about their sexual orientation).
Women and girls who have sexual contact with other females and men and boys who have sexual contact with other males can get and pass on STIs, so it's important that they know how to protect themselves.
From NHS.UK