OK.  I'm going to take a stab at trying to put together all the things that my mother told me growing up.

The first part involved educating me about the changes that happen in the female body during puberty.  Because my mother has a sister who started her period at age 9, this education for me began around age 7 or 8.  I was told these were all normal things.

Once I started having a period (age 10 or so), my mother started discussing sex.  She felt it was her duty at this point because she had a daughter who could become pregnant.  She talked about how it was normal to have feelings.  And she put things just how the article said -- that getting pregnant young could limit my life choices.  Her preference was that I would abstain from sex but if I chose to have sex, she wanted me to be comfortable enough to discuss birth control options with her -- preferably before having sex.  (My paternal grandmother echoed many of my mother's words during those years as well.)  When I said that I had no intention of having pre-marital sex, my mother countered with, "You say that now but sometimes you get caught up in the moment and all other thoughts are forgotten.  I just want you to be prepared for it."  My mother also stressed the importance of being in a caring relationship -- marriage was not a requirement.

I waited until college.  And before having sex, I went to the doctor first to get birth control.  Because that's what my mom would have wanted me to do if I had discussed it with her.  And because I knew that I wanted to finish college and that it would be difficult if I also had to care for a child.  (I have always been pro-choice but knew that that was a choice that would be difficult for me.)

I think the key is to give your girls a strong enough foundation that even if they don't discuss things with you, you know that they will make the best choice under the given circumstances.