Studies show that puberty is starting earlier and has dropped about three months each decade since the 1970s. Based on this newer starting age for puberty, girls in the U.S. are most likely to get their period around 12 years old.
The most probable explanation for why periods and breast development might be happening younger is that girls tend to weigh more today than they did a generation ago—and this higher body fat percentage is leading to earlier activation of the pituitary gland, which produces the hormones responsible for puberty.
The age at which most girls get their periods has fallen much more slowly since the '50s, but it remains a topic of medical interest and concern – among other reasons because earlier menarche conveys increased risk of breast cancer.
Your periods will start when your body is ready. This is usually between age 8 and 17, or 2 years after your first signs of puberty. Possible reasons for delayed periods include being underweight, doing lots of exercise (including dance, gymnastics and athletics), stress and a hormone imbalance.
Researchers and physicians hypothesized about possible causes for the increase in early puberty, such as increasing rates of obesity; greater exposure to endocrine-disrupting chemicals found in food, plastics, and personal-care products; and stressful or abusive home environments.
Studies in the decades since have confirmed, in dozens of countries, that the age of puberty in girls has dropped by about three months per decade since the 1970s. A similar pattern, though less extreme, has been observed in boys.
The average age for girls to start puberty is 11, while for boys the average age is 12. But it's perfectly normal for puberty to begin at any point between the ages of 8 and 13 in girls and 9 and 14 in boys.
First Period Symptoms
Growing pubic hair: Just after your breasts start to form, you'll probably start growing pubic hair. It will be soft and thin at first, but it'll get coarser over time. Your period usually arrives around one to two years after.
For most children, early puberty starts for no known reason. It can run in families. Sometimes there is a problem in the brain, such as an injury, a tumor or an infection. Early puberty can also be caused by a problem in the sex glands (testes or ovaries), the thyroid gland or the adrenal glands.
When your daughter starts to go through puberty, her gonads (ovaries) and adrenal glands (glands that sit on top of the kidneys) release hormones. These hormones cause the first signs of puberty, which are breast development, body odor, underarm hair, pubic hair and acne (pimples).
Most girls get their first period when they're between 10 and 15 years old. The average age is 12, but every girl's body has its own schedule. Although there's no one right age for a girl to get her period, there are some clues that it will start soon.
In Stage 2, physical changes begin. Between the ages of 8 and 13, girls typically experience: Their breasts begin to bud, and their areolas (pigmented area around the nipple) enlarge. Scant pubic hair appears.
Edmundo Escomel reported her case in the medical journal La Presse Médicale, including that her menarche had occurred at eight months of age, in contrast to previous reports that she had had regular periods since the age of three or two and a half.
Myth: menarche means the end of growth is near
The reality is that the average gain in height after menarche is about 7 cm (3 inches), and it is even greater for girls who menstruate on the early side of normal.
“It is not uncommon for girls to start their period as young as 8 or 9,” says Dr. Sara Kreckman, UnityPoint Health pediatrician. “This can be both emotionally and mentally challenging for girls this young, as well as their parents.”
Children with precocious puberty may grow quickly at first and be tall, compared with their peers. But, because their bones mature more quickly than normal, they often stop growing earlier than usual. This can cause them to be shorter than average as adults.
High protein intake elevates IGF-1 levels and promotes growth, which could accelerate the onset of puberty. Poor diet. Children with lower-nutrient diets tend to enter puberty earlier. A diet rich in processed foods and meats, dairy, and fast food is disruptive to normal physical development.
Your first few periods may be very light. You may only see a few spots of reddish brown blood. Anywhere from 2 to 7 days is normal. If your period lasts for more than 7 days, you should talk with your doctor.
That was the experience of Patrick Burleigh, who has a rare genetic mutation that triggers testosterone production far younger than normal.
When Does Puberty Start? Most females will start puberty when they're 8 to 13 years old, and most males will start between 9 and 14. But it can also be normal to start earlier or later.