Girls have been starting puberty earlier and earlier for several decades, and today it is not unheard of for girls to start their period at 9, and develop breasts before they are 11. Dr. Aksglaede (and her colleagues) in Copenhagen suggest this month in Pediatrics that the pattern seems to be speeding up. Girls in 2009 are already starting puberty earlier than girls did in 1993.
There have been many theories about why puberty is coming earlier - hormones in dairy products, extra calories, chemicals, pollution, heavier girls start their periods earlier, and even light exposure. The theory getting the most press these days seems to be exposure to chemicals, particularly those called plasticizers, in particular one called bisphenol A or BPA.
BPA is found in food and beverage containers including baby bottles and children's sippy cups. BPA seems to mimic estrogen the growth hormone that starts puberty, and the research suggests that we know it contributes to early puberty, we just do not know how much.
Early puberty is tough for girls and also tough on parents. When girls are starting their periods and getting breasts before they are 10, they need information and skills about what it feels like to have people look at you in a sexual way. Girls this age need to hear that there is nothing they are doing to attract the seual attention nor do they have to participate in anything they are not ready for. Have the talk!