How Female Puberty Works

Puberty in a girl is generally considered to start when she has her first menstrual period, also called menarche. This is a good marker to use because a girl's age at menarche can vary by quite a lot. In a group of girls studied in a state social care environment, girls of the same age exhibited as much difference as 3.5 years in developmental growth despite being 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) [source: Pryor, et al].

However, puberty starts before that, often between the ages of 10 and 14. Before menarche occurs, the hormonal makeup of the body changes, pubic hair appears and breasts begin developing (we'll talk more about that later). A girl's average age at the time of her first period is 12 years old. Periods can come earlier or later than that, however, and the average age of menarche has been dropping. Girls for whom menarche occurs after age 13 tend to have more irregular ovulation cycles until age 18 or 19 [source: MedicineNet].

During puberty, a girl may experience a remarkable change in height: Girls often grow as much as 3.5 inches (8.9 centimeters) in height a year during puberty [source: Morgan, et al]. Girls can gain almost one-fifth of their final adult height during puberty, and the first period usually follows the first major growth cycle by six months [source: MedicineNet].

The first period correlates with a sort of "halfway point" in adolescent bone growth. The bones will have widened and begun to lengthen, but they aren't fully mineralized, making them more vulnerable to fractures. This is bad news because girls (and boys) can often be clumsy during puberty. But they can't be blamed -- bodily growth doesn't happen everywhere at the same time. First the hands and feet grow, meaning lots of falling over and dropping things. Soon enough, though, the rest of the body will even out in proportion, and the pubescent girl should be able to walk across a crowded cafeteria without catastrophe.

In the first stage of puberty (which often occurs sometime between the ages of 8 and 11), the only signs of puberty are occurring inside the body, as ovaries react to hormones such as LH and FSH and begin developing estrogen-producing capabilities.

The second stage of puberty generally takes place when a girl is 11 or 12. Breasts begin to grow, or "bud." Buds exist when the areola darkens and rises and some transitional breast tissue exists. This generally comes before all other visible signs of adolescence, though it's not uncommon for pubic hair to begin growing before the breasts begin to develop. A growth spurt will occur.

In the third stage of development, growth of the breasts and pubic hair continues. Hair may have begun to show up in the armpits, and the vagina grows in size. This stage usually covers a girl aged 12 or 13 (though any girl between the ages of 9 and 15 could also pass through this stage). By this stage in development, menarche will occur for seven out of 10 girls [source: LiveStrong]. Once the body receives its signal from the brain to undergo puberty, it takes less than three years for menstruation to occur.

In the fourth stage of puberty for girls (often around ages 13 and 14), the accelerated growth of her height will usually slow down. The adolescent's level of body fat will reach higher adult levels, tapering off at around 26 percent body fat. Pubic and underarm hair will continue to grow fuller and more coarse. If the first period has occurred, ovulation may be irregular as it establishes its rhythm. While it's now common for girls at 12 or 13 years of age to have already had their first periods, it wasn't always so. In fact, just over 100 years ago, most girls were 15 when they had their first periods (changes in nutrition, health and the environment are believed responsible) [source: Stoppler].

Stage five represents the fully matured girl (usually around ages 14 to 17, though not uncommonly up to age 19) who has passed through all preceding stages of puberty. The girl has likely reached her maximum adult height by this time. Breasts have likely reached their full size, and pubic hair is fully developed. Periods and ovulation occur regularly. The cardiovascular, skeletal and muscle systems are all fully developed.

Breast development in most girls begins between the ages of 7 and 13. It's often the first physical marker of the onset of puberty. (If a girl is overweight, it may appear that her breasts have begun budding when this isn't the case.)

The first sign of adult breast development is an enlargement and possible darkening of the areola around each nipple. Slight discomfort or tenderness in the breast area isn't uncommon, but it goes away after a few months or so. This tenderness is caused by the influx of hormones that occurs in early puberty. The rapid growth in the breast area will stretch the skin, often causing the area to itch. Scarring in the form of stretch marks can occur.

Both breasts may not develop at an equal rate, and one will often begin before the other. Breast growth occurs one to two years before menarche and continues for about four years after it.

In stages, breast growth tends to advance as follows:

Anywhere from six months to three years after the onset of puberty (as marked by breast budding), a girl will experience her first period, or menarche. This is when the uterus sheds its lining, which is accompanied by blood.

Between the time the breasts begin to develop and menarche, a girl will likely have a significant growth spurt, gaining several inches in height (as much as 4 or more inches (10.2 centimeters) in a year) [source: Moses]. A girl who has entered puberty will also gain weight. There may be a connection between excess body weight, the early onset of puberty and the onset of menstruation because the body basically perceives that the nutritional needs for a pregnancy can be met.

Several months before menarche, girls will begin noticing white vaginal discharge. This is normal and is essentially the precursor to the first period, as the uterus develops and begins discharging fluid.

From the point of first menstruation, a girl's periods will likely be irregular for several years. Even when the menstrual cycle is regular, girls may have cycles as short as 15 days or as long as 40 days. The amount of her menstrual discharge may also vary from month to month, but on average a girl will lose about a quarter-cup of blood during her period. It can last from three to 10 days, with heaviest flow usually occurring on the days two and three. If a girl feels like she's having an abnormally heavy period, she should contact her doctor.

Cramping, pain and even nausea occur very commonly during menstruation. This is a result of the uterus contracting to expel its lining. There is no single method of relieving the cramping that works for everyone, so girls will have to experiment with various combinations of rest, activity, diet and medication until they find something that works best for them.

Girls may also experience symptoms of premenstrual syndrome (PMS) such as aches, pains, bloating and moodiness. Over-the-counter pain relievers, as well as restricting caffeine and salt from the diet, may help alleviate these symptoms. (To get the whole story on PMS, give How PMS Works a read.)

Ovulation doesn't begin automatically with menarche -- it can be another two years before a girl is capable of conceiving a child.

­Of all the changes in store for a pubescent girl, acne may be the only one that doesn't serve some greater purpose. Acne blemishes are caused by the blocking and inflammation of pores in the skin that produce sebum. Sebum is an oil that helps moisten the skin and keeps bacteria from getting in the body. Sebum is produced in the body and then travels up the follicle to the skin's surface, where it mixes with salts, dead skin cells and other matter to form a type of protective coating.

Unfortunately, however, when sebum mixes dead skin cells while still inside the follicle, it can block off the follicle, get infected by bacteria (Propionibacterium acnes, or P. acnes for short)and become inflamed. End result: zit.

It's a hard enough time in a girl's life: Her entire body is changing both inside and out, she feels like she's especially under the microscope, and now her skin is rebelling against her.

Girls tend to have fewer problems with acne than boys do during puberty. However, after puberty and throughout adulthood, girls are more commonly afflicted with acne (perhaps making pubescent acne that much more frustrating).

The best ways to prevent acne during puberty (and beyond) are gently washing your face, completely (without hard scrubbing!) removing makeup each evening and showering after working up a sweat. Also, don't pick at your face or touch it more than necessary, as this will agitate the skin and lead to more breakouts.

If any particular food seems to cause acne outbreaks, it is best to just trust your own judgment and avoid it for a while to see if that helps your skin. Remember: There is no single cause of acne, and likewise you often require a mix of preventive measures to stop it.

To treat acne, try products containing benzoyl peroxide or salicyclic acid. These substances dry out skin, kill the bacteria and help the skin shed its dead skin cells. Start off with small amounts of these products to give your skin the chance to get used to the medications. (Need to learn more about acne? Try How Acne Works.)

Most cultures mark the rites of passage in life with special ceremonies, observations or events. The first of these is usually an event for the naming of the child, followed for girls usually by a rite marking the transition to adulthood.

Customs vary throughout Africa according to region, nation and tribe. Villages in Ghana separate girls for several weeks from the rest of the village once they have their first period. During this time, girls are instructed in sex education and social mores regarding courtship and nonromantic relationships with males. Then a village-wide ceremony and celebration takes place, presenting the adolescent girls to the community.

Rites have significance beyond just honoring or acknowledging the change in the girl's life. Some cultures use this as a chance to teach ethics and sexual morality to girls, or to choose a mate for the girl. A Brazilian tribe (Urubu-Kaapor) crops a girl's hair at her first menstruation and separates her from the village for fasting and education. She can't be married until her hair has grown back to shoulder-length, giving her time in the community to develop into an adult.

Native American tribes, such as the Navaho and the Apache, have their own puberty rites of passage for girls. The separation time for the girl experiencing her first period was as much to honor the transition to adulthood as it was to protect the village from the calamities superstitiously blamed on such an event.

Until the 20th century, Jewish males had a ceremony observing the transition to adulthood, but not girls. Now, Jewish females may participate in a bat mitzvah, which is a ceremony (and often a party) that occurs on a girl's 12th birthday. The status of adulthood and "bat mitzvah" (which translates to "daughter of the commandment") is conferred upon the 12th birthday with or without the celebration.

Though Islamic families and communities vary greatly in their cultural practices, the Quran instructs Muslims to forewarn their daughters at 9 years of age about the arrival of menstruation. Additionally, girls are taught that from that point on, they will be accountable to God for their actions. The Quran also instructs husbands and men to "keep away from women during menses" which has been interpreted in some cultures as not allowing menstruating girls and women to pray, fast or enter a mosque [source: Quran Today].

Puberty develops the mind as much as it develops the body. Whereas children (under the best of circumstances) live relatively carefree lives, girls who have gone through puberty may suddenly feel they have the burden of the world on their backs. On the other hand, the loss of childhood "innocence" also goes hand-in-hand with the development of a mind capable of processing higher thoughts and abstract concepts. As their entire world has changed from within them, girls must find and establish a new identity. This search begins long before their bodies stop evolving into their final adult forms.

Self-awareness increases and may be mistaken by others as self-obsession, but this is completely normal. An adolescent girl must closely examine her own beliefs and feelings in order to find her place and roles within the world. Girls will likely also feel self-conscious, especially in light of crude remarks or teasing by boys who are shorter and less developed and, in many cases, frankly terrified of the towering women now walking among them.

Existing sleep patterns will probably get turned on end during puberty, as girls may suddenly get enough rest to make old housecats look spry and lively by comparison. Moods may become erratic, due to hormonal fluctuations and the stresses of transitioning into adulthood in a world that isn't sure when to stop treating adolescent girls like children. Mood changes may also be caused by the presence of parents, who have by now fully developed into embarrassing life forms. Puberty offers a perfect window of opportunity to rummage through parents' belief systems and rearrange things to their liking. Many of the lessons and beliefs handed down to girls by parents as inalienable truths throughout childhood may now seem unjust, hypocritical and logically unsound. This new questioning mindset should be fed with all the information it craves. It also presents a good opportunity to broaden educational horizons and explore new subjects, philosophies and the lives of heroic women throughout history.

Clothing and appearance will become more individualized, as girls experiment with their physical image and how it can affect how a girl either blends in with her peer group or stands out from the crowd.

As a girl goes through puberty, she'll experience many exciting changes and many troubling moments. This time in life can easily be overwhelmed by depression, anxiety or "adult problems" like pregnancy or sexually transmitted diseases. Parents, guardians, friends, mentors and teachers all play important roles in providing a framework of support and education to girls who face the potential pitfalls of adolescence.

As a girl becomes more aware of her own personal appearance, her changing body and society's near-obsession with the female form, there will be a greater risk that she'll develop an eating disorder, such as anorexia nervosa (self-starvation) or bulimia (overeating and purging). During this turbulent phase of life, some girls may also have difficulty expressing complex feelings and emotions and may attempt to do so through self-cutting, burning or other forms of self-mutilation. If a parent suspects these issues are in play, he or she should contact a mental health professional or family doctor.

Girls begin pushing their own behavioral boundaries and taking increased personal risks. While some girls may push themselves academically or athletically, others may begin experimenting with tobacco, theft, sneaking out, sex, drugs and alcohol. This, too, is a normal part of growing up. Of course, there may be a problem if these behaviors continue beyond an experimental phase. Ideally, girls will have discussed these and other adult issues with their parents or another clear-headed adult before they're confronted with potential sources of life-changing trouble.

Girls may begin experimenting with masturbation and showing an increased interest in all things sex- and courtship-related. This is totally normal. Increased feelings of anxiety or guilt about these feelings may also exist.

Girls passing through adolescence become more aggressive and competitive with one another, and may attack other girls through slander, gossip and ridicule. Pressures from heavier school workloads, shifting social networks and physical strain just from all the growing make this an especially hard time for many girls.

To learn about the male side of puberty, PMS and acne, try the links to HowStuffWorks on the very next page.