O.:
I have read the responses given and want to say that there was plenty of information to choose from, plenty of great advice. I was looking for some specific information because I didn not wish to belabor what had already been wirtten.
Let me say I understand where you are coming from. As a mother of three girls, 28, 26, and 12, I have seen an evloution in the need for greater and sooner preparation since my own teen years (I am also the eldest of three girls) through this present day.
It is true that your daughter may already know more than you realize and more thatn she maturely knows what to do with. There may also be some things which she does not know, or refuses to believe can happen to her.
As a community health educator, I have learned that the advice given for many years is terribly insufficient. Know this, the decision to have random or uninformed sex can become a matter of life and death. It is no longer simply and issue of antibiotics, birth cotrol pills, a visit to planned parenthood to end an unwanted pregnancy, or a visit to a hospital or fire station to surrender and unwanted infant.
Today, if you "catch" a baby, you may also catch an STI (sexually transmitted infection), veneral warts (perhaps leading to cervical cancer), herpes (a life-long and painful condition), or HIV (at a sadly, ever more increasing rate).
Consider having your child be a part of the information gathering process through web searches and other information searches. This way you can learn together (you will be surprised, amazed and even struggle with disbelief at some of what you will find out)and you may prevent coming off as a know-it-all dictator. You may say somthing like,"you're at an age whare you need to be informed about sexual issues and I'm at a place where I need to update and expand my knowledge, so let's do it together." This opens up channels for discussion of wht is being learned. Don't be afraid to appear human, i.e., vulnerable.
It is possible that some of the information gleaned may be frightening, but is is better that she be frighteningly informed rather than risk her life being uninformed. Also the fear can be abated by making healthy informed choices. Mere minutes of pleasure versus lifelong, life-threating consequences.
She may also try to take the position, since the information and statistics are about other people, that the negative consequences happen to others and will not happen to her. It may help to inform her that to other people, she is other people so that means that she is not immune to being affected or infected and it can happen to her. These diseases are not transmitted by engraved invitation, with prescision, or selectively. It can be likened to a game of chance or Russian roulette.
The pill alone PROTECTS your chlid from pregnancy alone (and this is less than 100%). PROPER condom use PROTECTS against disease (and this is less than 100%). Abstinence PREVENTS both, and is 100% effective. The safest sex is no sex, and grown up actions can be accompanied by grown up consequences.
After saying all this, I can also share from experience that the final choice will ever remain your daughters and your only benefit may be the knowledge that you did what you were morally required to do as a loving mother.