I don’t think that any parent relishes the thoughts of sitting their child down to discuss sex with their teenager and likewise no teenager really relishes the idea of having to sit there listening to their parents talk about sex.
You should try and not be offended, if your child looks horrified and tells you that you are embarrassing them. Remember, no matter how much they protest they will be glad that you have made the effort to talk to them about sex and it will help them to know that they can broach the subject with you again if they have any other questions.
It can be helpful to try and make sex a part of regular conversation. Mention it casually if the subject comes up on TV or while listening to the radio. It’s important that your child isn’t afraid to come to you about something they may be confused about.