You cannot control when your child will go through puberty.
Scientist have studied this for years and there have not been any verified theories.
Each person has their own hereditary histories, they have social situations and then it is just biological.
I am almost 50 and I remember very distinctly, my mother and my elementary school, spoke with us about our bodies maturing and getting ready for our menstrual cycles in the third grade. I think they did this way back then, because even then they knew some girls had bodies that matured early and they needed to give all of us a heads up.
There have been studies with so many results, it makes sense that there can be many theories. In the 60's and 70's they said it was due to mothers working out side of the home and young girls having to take over mom duties(Oy vey!)
In the 70's and 80's they said it was girls in households where divorced mothers had multiple boyfriends.. (again notice they did not mention divorced dads with lots of girlfriends),
Then in the 90's they said it was hormones in the meats and milk , which now has been proven to not be Totally true. (Your child would have to drink a dairy case per day for the rest of their lives for this to occur).
And now in the 2000's they are saying it is due to childhood obesity..
What makes the most sense is that every child is different with all sorts of variables. As parents if our goal is to make sure our children eat a healthy variety, are active with lots of play, and stable house holds, they will be as healthy as we can make them and yet there are things we cannot control. Biological hereditary.
So what we need to do is always educate our daughters. Be honest about and not ashamed about the truth. Use the real language, so that they will have a heads up.
http://www.livescience.com/health/070904_bad_puberty.html
Here is an interesting article.
http://www.livescience.com/health/070904_bad_puberty.html