First Physical Signs

Breast budding is the first clear sign of puberty in 85 to 95 percent of girls and may initially start on only one side or the other. The teen growth spurt usually starts at the same time as the breasts start to grow.

The appearance of pubic hair is commonly next. In a recent study of 8- to 9-year-old girls, 5 percent of Caucasian girls and 15 percent of African American girls had some breast development. In the same group, 8 percent of Caucasian girls and 34 percent of African American girls had some pubic hair.

Breast development before age 8 is considered early and should be checked by a doctor. At the other extreme, no breast development by age 13 is thought to be late and should also be evaluated.

First Period

The first menstrual cycle (menarche) occurs approximately two to two-and-a-half years after the appearance of breast buds. The average age of menarche in the United States is 12.5 years.

Researchers suggest that the decline in the age of menarche during the last hundred years is due to improved nutrition, but they don’t expect that this age will continue to drop. Females with low weight and low body fat tend to have delayed menarche.

Regular Periods

The time from menarche to regular periods tends to be about 14 months, but some young girls start being regular at once. The time between menarche and painful periods (presumably ovulatory cycles) is about 24 months.

Menstrual cycles vary quite a bit and cannot be counted on as a method of birth control.

Consider seeing a doctor if you have:

• Infrequent periods, especially when associated with severe acne and excessive body hair. This could indicate a condition called polycystic ovary syndrome.
• Periods that consistently occur sooner than every 28 days.
• Excessively heavy bleeding.
• Periods that last more than seven days.

Last Reviewed: October 2019