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How does puberty begin in girls?

Puberty in a girl is generally considered to begin with the onset of her first menstrual period, known as menarche. Menstruation is a good marker to use because the age of a girl at menarche varies quite a bit. In a study of a group of girls in a state social care environment, girls of similar age demonstrated as much difference as a 3.5 year difference in developmental growth. These girls were of the same chronological age (meaning one girl might be two years ahead of the average when menarche occurs and another girl two years behind the average even though they're both the same age.) yet experienced the first menstrual period at different ages.

However, puberty is already gearing up in a girl before the menstrual cycle begins, initially kicking in often between the ages of 10 and 14. Before menarche occurs, the hormonal composition of a girl's body changes, pubic hair is visible and breasts begin growing. The average age of a girl at the time of her first period is 12 years old. Periods may arrive earlier or later than that. However, the average age of menarche has been decreasing. Girls who experience their first period after the age of 13, tend to have greater frequency of irregular ovulation cycles for the first several years until reaching the age of 18 or 19.

During puberty, a girl may go through a remarkable change in height: Girls frequently experience as much as a 3.5 inch (8.9 centimeters) growth in height each year during puberty. A girl may add almost one-fifth of her final adult height during puberty, and her first period often arrives six months after her first major growth cycle.

The first period links with a sort of "halfway point" in a girl's adolescent bone growth. Her bones will have widened and begun to lengthen, but they are not yet completely mineralized, making them more susceptible to fractures. This is bad news because teenagers can often be awkward and clumsy during this time of growth and change. But they can't be blamed-bodily growth does not take place everywhere at the same time. The hands and feet grow first, increasing the potential for much falling over and dropping things. Soon enough, the rest of the body will be in proportion, and the pubescent girl will be able to glide across a crowded cafeteria without catastrophe.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.