Puberty in Girls - The Transition into Womanhood

Puberty in girls is characterized by skeletal growth as well as the development of a girl’s primary and secondary sexual characteristics. Girls begin puberty earlier than boys by about 12 to 18 months.

a teenage girl carrying books

Skeletal Growth

Girls grow in height during their years of puberty due to a growth hormone released by the pituitary gland. This gland is situated at the base of the brain. Girls experience rapid skeletal growth around age 12, whereas this usually begins around age 14 for boys. A girl’s hands and feet will also grow at this stage.

Primary Sexual Characteristics

A woman’s primary sexual characteristic is her ability to become pregnant and bear children. Around age 13, girls begin to have a monthly period. This is a period of vaginal bleeding that usually lasts for a week. It is caused by cycles in the production of a hormone called estrogen. This is what marks puberty in girls.

diagram of a woman's uterus

Each month, a woman’s uterus (womb) prepares for pregnancy. It builds up its inner lining. If a woman doesn’t get pregnant then this lining and the unfertilized egg that was released by the ovaries are discharged through the vagina. This is what is seen as blood during a period.

Not all girls experience a period around age 13. With some it can be as late as age 15 or 16.

Extremely thin girls usually start having their period later than average. Overweight girls usually start earlier. However, if a girl gets her period early, it doesn’t necessarily mean that she needs to lose weight.

As a girl grows older, her menstrual cycle gradually becomes closer to a 28-day cycle. It can, however, be unpredictable during the first few years but it does normalize by her twenties.

Feelings of discomfort such as depression, irritability, abdominal cramps and breast tenderness gradually stop as a girl leaves teenage hood. Some girls never experience these discomforts.

Secondary Sexual Characteristics

diagram of development of a girl's sexual characteristics

Puberty in girls is clearly visible by the development of the breasts. This is due to the hormones called estrogen and progesterone. Breasts start developing around age 10 or 11. By age 14 to 15, most girls’ breasts are nearly fully developed.

Puberty in girls is also characterized by the growth of pubic hair and the widening of the hips. The hips widen in order to ease the process of child birth.

Body hair also increases. The hair under the arms and on the legs grows. Some girls also grow hair around their nipples.

diagram of the development of a girl's breasts


A girl is not necessarily fertile after she’s had her first period. The ovaries usually don’t release eggs until 12 to 18 months after regular menstruation.


All of the changes in a girl’s body during puberty are due to the production of two hormones called estrogen and progesterone. These hormones are produced by the ovaries.

Puberty in girls usually ends around age 14 or age 15. For some girls it can last until age 17. A girl will still grow in height and weight after puberty but usually only two inches in height after her first period.

By this time, the girl’s voice will have deepened and her body hair will be darker, thicker and curlier. By her early twenties, a girl’s breast will have fully developed.

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