When I was growing up..
I remember the grown-ups would hide everything "negative" from us children. Well why not uncover what we need to know? The point that I am trying to arrive at is; if you are a parent, keeping certain things a secret is a positive action to act upon where as on the other hand if you leave out the important topics I guarantee the out come won't be what you were expecting. Our generation needs to be more aware of certain situations such as sex because, well I know in my case I was a very young girl when I learned about sex and sexual diseases. With that being said I think that my parents were the reason why I waited until I was 18 to encounter any type of sexual involvement. I personally think it is best to be the one who speaks to your child about sex instead of their friends or sex-ed. Not only do girls need to know when is the proper time to conceive a child, they also need to know about birth control and condoms.
I myself am not a parent so I can't speak for how they feel about speaking to their child about sex but, what I can do is tell you is; if you don't tell them everything then there is a good chance that they will find it out on their own and you will have to deal with it then. I will end this post with this; if your uncomfortable with talking about sex with your child you should always remember that you are the one they will be coming to for answers their entire life.