Girls in the United States are beginning menstruation at increasingly younger ages — a shift that has drawn growing concern from scientists and public health experts. Recent research analyzing data from more than 71,000 participants shows that both early menarche(before age 11) and very early menarche (before age 9) are becoming more common across the country.
This trend appears to be most pronounced among racial minorities and lower-income groups, suggesting that environmental and social inequalities may be influencing biological development. In addition to earlier onset, the study also found that girls are taking longer for their menstrual cycles to become regular, indicating deeper disruptions in hormonal and physical patterns.
The most significant factor contributing to this change is higher childhood BMI, as rates of childhood obesity have continued to rise. Increased body fat can affect hormone levels, particularly estrogen, which plays a major role in triggering puberty. However, BMI alone does not explain the entire pattern.
Researchers also point to stress, trauma, diet, and exposure to endocrine-disrupting chemicals — substances found in plastics, cosmetics, and processed foods — as contributing factors. These chemicals can interfere with the body’s hormonal systems, potentially accelerating the timing of puberty.
Early menstruation has serious long-term health implications. Girls who begin their periods at younger ages face an elevated risk of breast, ovarian, and endometrial cancers, as well as heart disease and stroke. The longer lifetime exposure to estrogen also increases the likelihood of developing reproductive conditions such as polycystic ovary syndrome (PCOS).
To help reduce risks, experts recommend that girls and young women maintain a balanced diet, engage in regular physical activity, and manage stress through healthy coping mechanisms. Limiting exposure to harmful chemicals in everyday products can also make a difference.
Yet, individual action alone is not enough. Scientists and advocates emphasize the need for systemic change, including stricter regulation of chemicals known to affect hormonal development and expanded public health programs that address childhood nutrition and stress.
Ultimately, protecting future generations will require a collective effort — one that combines education, research, and policy reform to ensure that all children, regardless of background, can grow and develop in healthy environments.