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17 September 2014
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Grown-up girls

Girl looking in mirror
Changing shape

Growing taller is one of the first external signs that a girl is experiencing puberty. This is just the beginning.

Kicked off by sex hormones, the growth spurt is closely related to the arrival of periods. Once the ovaries are mature, the legs have generally finished growing. Any increase in height after periods have begun, usually comes just from the torso. A general rule is that a girl will grow no more than 6cm after her first period.

By 14, on average, the spine has also finished growing. Lastly, the bones of the pelvis widen and become smooth, in preparation for childbirth. This can occur up to the age of 18 or even later.

Video clip Watch a girl's skeleton grow
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Changing shape

Before puberty, boys and girls have a very similar physique. But they both change shape noticeably as increasing amounts of sex hormones sculpt their bodies in different ways. Boys experience a large degree of muscle development after the skeleton has finished its growth.

In girls, this stage is much less pronounced. Instead, the female sex hormone oestrogen triggers the laying down of fat. This is concentrated at the hips and bust and is perfectly normal. It is less noticeable in girls who exercise a lot.

Interactive body See a girl's face turn into a woman's.
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A new face in the mirror

As a teenage girl grows taller and heavier, she also experiences growth in the bones of the face. These changes are less dramatic than they are in boys, but they do change appearance as the face becomes longer and more angular.

The first extension is from the ridge of the nose down to the mouth. As the cavities inside the face increase in size and the vocal chords lengthen, girls' voices drop a tone or two in pitch. But this is a minor change compared with the octave drop experienced by boys.

Not only do girls grow up, they also grow out. Find out more about breast development .

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