The first changes of puberty are not visible ones. They are the changes in hormones resulting from activation of the hypothalamus -- the regulator in the brain, and the response of the ovary with secretion of sex hormones. As experienced parents know, 'moodiness' occurs approximately one year before the obvious physical changes in puberty occur. Other early signs of puberty are body odor and vaginal discharge. Again, these early changes can occur a year or more before the appearance of secondary sex characteristics (i.e., breast development and pubic hair).
Breast budding is the first sign of puberty in 85 to 95 percent of girls and may initially start on only one side or the other. The 'growth spurt' of adolescence usually starts at the same time as the breasts start to grow. The appearance of pubic hair is common next. In a recent study of 8 to 9 year-old girls, 5% of white girls and 15 percent of African American girls had some breast development and 8 percent of white girls and 34 percent of African American girls had some pubic hair. Breast development before age 8 is considered early and should be checked out by a physician. At the other extreme, no breast development by age 13 is thought to be late and should also be evaluated.
Menarche (the first menstrual cycle) occurs approximately two to two-and-a-half years after the appearance of breast buds. The average age of menarche is the United States is 12.77 years. The decline in the age of menarche during the last hundred yeas has been attributed to improved nutrition. It is not expected that this age will continue to drop. Females with low weight and body fat tend to have delayed menarche.
The time from menarche to regular periods tends to be approximately 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. This varies quite a bit and cannot be counted on as a method of birth control. Infrequent periods, especially when associated with sever acne and excessive body hair should be evaluated for the possibility of polycystic ovary syndrome. Periods which occur consistently less than every 28 days, excessively heavy bleeding, or periods which last more than seven days should also prompt a visit to the doctor.
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Nancy Brown, PhD reviewer
Last Revised November 2012
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