When does breast development typically begin in girls in the United States?

Breast development in girls typically begins around the age of 10 in the United States. This developmental milestone, known as thelarche, marks a key point in the onset of puberty, where hormonal changes prompt physical changes in the body.

The start of breast development can vary among individuals but generally falls within a range that begins between ages 8 and 13. The average onset around age 10 aligns with data collected from health studies and growth charts, which have shown that early signs of puberty, including changes in breast tissue, start to appear around this age for many girls. This timing is influenced by both biological factors and environmental conditions, including nutrition and overall health.

Understanding the typical age for the onset of breast development helps to frame discussions about puberty and the associated physical, emotional, and social changes that occur during this crucial period of growth.