If it seems to you that girls are growing up faster than a generation ago, you may be right. In fact, girls are starting to have their periods earlier and budding breasts are emerging earlier than they did even a generation ago.

So what’s the big deal about leaving girlhood behind sooner rather than later? And what might you do to stop the progression in your youngest daughters?

Maturing earlier is concerning for several reasons. Early puberty is a well-established risk factor for developing breast cancer later in life. For girls, it’s also associated with risky behaviors in later adolescence, including drinking, drug abuse and unprotected sex, behaviors that may have lifelong consequences. Girls who mature early have also been found to have higher rates of depression and eating disorders.

So what’s normal? The start of puberty can vary widely, but typically the breasts begin to bud around age 10. Pubic hair appears within the next year and menses begins sometime in the 2 years after that. In the U.S., most girls begin menstruation between ages 12 and 13.

However, researchers have found that breast development, on average, is now beginning for many girls about a year earlier than a generation ago, both in the U.S. and in Western Europe. By age 10, about half of girls in the U.S. will have started breast development. Girls are also getting their first menstrual period several months earlier than their mothers’ generation.

Scientists are exploring a variety of possible reasons for the changing age of puberty, which prior to recent decades hadn’t largely changed for centuries. They’re focusing on factors that influence a girl’s production of hormones; it’s the interaction of these factors that may help explain earlier sexual development. Girls who are overweight or obese tend to mature earlier. And more girls are obese now than in previous generations. But that’s not the whole story. Normal weight girls are also maturing earlier.

Being born prematurely or at a low birth weight, or both, also seems to put a girl at risk for reaching puberty earlier. Both of these events cause the hormone insulin, which regulates blood sugar and therefore body weight, to be used differently in the body. As more babies are born prematurely in the U.S., researchers expect this to affect more American girls.


Finally, researchers are looking at the influence of chemicals found commonly in our everyday environment (many in plastics), such as bisphenol A (BPA) and phthalates, which are called endocrine-disrupting chemicals (EDCs), to see what role they may play in sexual development. These chemicals may be influencing change during critical periods of development such as during fetal life and adolescence. While it hasn’t been proved in humans, it’s been shown in laboratory animals that even very small amounts of these chemicals can affect sexual development. It may take years before there is conclusive evidence about the effects of chemicals, nutrition, birth weight and prematurity on when girls, and boys for that matter, begin puberty.

The best approach is a practical one: minimize those factors thought to be involved in early puberty. Eat healthfully—lots of fruits and vegetables, whole grains and lower fat protein sources—and limit junk foods, especially those high in fats. This will help everyone in your house. Help yourself and your family by being active every day. Take a walk or bike ride after dinner and plan a physical activity the whole family can enjoy for the weekend. This will help everyone maintain a healthy weight and a strong sense of wellbeing for life.

If you’re pregnant, get regular prenatal care to curb your risks of having preterm labor or a baby born smaller than normal. Don’t smoke when pregnant and avoid second-hand smoke, as tobacco exposure in pregnancy is linked with early puberty.

Go green and organic as much as possible (see Live Green). Reduce your exposure to endocrine-disrupting chemicals. Use personal care products that don’t include phthalates. Switch to glass, ceramic or stainless steel containers rather than plastic for food storage and cooking to avoid BPA. Use wax paper rather than plastic wrap. Don’t microwave food or heat food in plastics; rinse foods in cans before cooking or serving them, as cans are often lined with BPA. Swap vinyl shower curtains for cloth ones and get rid of old plastic toys and baby bottles. The Consumer Safety Product Improvement Act that went into effect in early 2009 bans lead and phthalates in baby bottles and new toys.

About this Author: Catherine Ruhl, CNM, MS, is director of women’s health for AWHONN in Washington, DC.