However you bring up the topic of sex and relationships, listen to what your teenager has to say. You can then use this to let the conversation develop.
For example, if they mention condoms, check that they know why it's important to use them, where to get them and how to use them.
Talking about sex and relationships with your teenager won't make them want to start having sex, but it will help them look after their sexual health when they do.
Try to listen calmly, even if what they say surprises you or you disagree. Let your child know your opinions, but reassure them that you trust them to make their own decisions.
If you lose your temper or criticise them, they might feel like they can't talk to you in the future.
Ask your teen what their friends think
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?"
You could then talk about why it's OK not to have sex, and where young people can get contraception if they are planning to have sex.
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 programme, or a celebrity in the news. For example, you could say, "What do you think about the fact they've had sex?"
Listen to your child's answer. You could then talk about why it's important to use a condom and contraception to protect against sexually transmitted infections (STIs) and pregnancy. Make sure your child knows where they can get them. Don't sound judgemental or critical.
Find out how to talk to your pre-teen child about sex.
Find out what they're learning about sex at school
Ask your teenager what they're learning about sex and relationships in school lessons. Ask 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.
Listen to what your teen thinks about sex
Ask your teenager how they feel about things, such as 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?"
You can use this discussion to talk about the risk of pregnancy when a boy and a girl have sex, and about getting contraception ready before having sex.
You can also discuss who your child thinks should be responsible for contraception. Make sure they understand that it's up to both partners to think about using condoms and contraception.
Make sure you know the facts about sex
Sex is a large topic. It covers how our bodies work, pregnancy, relationships and feelings, types of contraception and where to get them, STIs, tests, treatment and more.
If you're confident in your knowledge of these topics, you'll be able to answer your child's questions more readily.
If you don't know something, say so, but let them know you'll find out. Look up the information and share it with them, or look it up together.
NHS Choices, which has lots of information on sex and relationships, is a reliable source of information. Other organisations include:
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 (to tell you about their sexual orientation).
Whether you have sexual contact with men or women, you can get and pass on STIs, so it's important that they know how to protect themselves. See sexual health for women who have sex with women and sexual health for men who have sex with men for more information.
If your child is gay, they still need to know about contraception. People who identify as gay or lesbian might have sexual contact with people of the opposite sex, so it's important that they know about contraception and how to avoid unintended pregnancy.