Girls are maturing earlier now than ten years ago. That's not necessarily an advantage, according to research.

Norwegian girls are reaching puberty earlier

A study from Norway shows that the average age for girls to start puberty has decreased by almost 3 months over the last ten years. Researchers are concerned about the trend.

Girls have their first period at some point between 9 and 17 years of age.

Most girls start menstruating when they are around 13 years old, which has been the pattern since the 1950s.

Now a new study from Bergen indicates that the average age for menarche – when girls get their first period – has decreased by about 2.8 months over the course of a decade.

Even though the change is only a matter of two and a half months, the researchers are concerned by the trend.

Ingvild Særvold Bruserud is a researcher and PhD candidate at the University of Bergen and the Children and Youth Clinic, Haukeland University Hospital.

The drop is not dramatic, and the age for first menstruation among Norwegian girls is still around age 13, Ingvild Særvold Bruserud tells Helse Bergen. She is one of the researchers behind the study.

“These are interesting findings because we don’t know why this change in puberty is occurring, or whether it’s a trend that will continue,” she says.

The trend is also happening in other parts of the world, including Denmark, where a study shows that Danish children are reaching puberty earlier than their parents did.

Breast buds are first sign

Puberty in girls means growing breasts, first menstruation, pubic hair and pimples.

The breasts usually come first, then the period. The girls start to grow in height almost at the same time as their breasts start to develop.

In boys, puberty begins when the testicles get larger, which usually happens around the age of twelve.

Did you know...

that there’s a word for girls' first menstruation?

Researchers call it menarche and it is the first bleeding from the lining of the uterus. Menarche usually occurs between 11 and 14 years old.

The average age of menarche for girls in Oslo, the capital of Norway, is 13.25 years old.

150 years ago, girls were almost 16 years old at menarche

The only information we have about puberty trends in Norway is from a study that shows when girls started menstruating in the period 1861 to 1974.

The study shows that the average age of first menstruation for girls in Oslo decreased from age 15.6 in the middle of the 19th century to age 13.3 in the middle of the 20th century, according to the Journal of the Norwegian Medical Association.

Over the course of 150 years, the age that Norwegian girls get their first period has dropped by almost three years.

Since the end of the second world war and until the first growth study in the mid-2000s, menarche has remained fairly stable at just over 13 years old.

In the last few years, the girls have become younger, with the average age at menarche now 12.9 years old.

Early puberty problematic

The onset of puberty is experienced as a turning point for many teens. We go from being children to becoming adults – or at least our bodies do.

But puberty can be problematic if is starts too soon.

Facts about the Growth Study

  • From January to June 2016, the second Growth Study in Bergen was conducted at six different schools in Bergen municipality. The main purpose has been to map the development of puberty in healthy children and identify factors that can influence such development.
  • A total of 1184 children and young people aged 6-16 participated, of which 678 were girls.
  • In addition to the external signs of puberty and ultrasound examination, the study measured weight, height, thickness of skin folds and abdominal circumference, in addition to taking blood samples of all the children in connection with the examinations.
  • The study is the first of its kind to be conducted in Norway.
  • The onset of puberty is defined by breast development in girls and increasing testicular volume in boys.

Source: HelseBergen and

Studies have shown a link between early onset of puberty and several unfortunate health consequences, according to Bruserud.

"Cancer, cardiovascular disease, type 2 diabetes, obesity and overweight are some of the potential problems," Bruserud tells

It's important to point out that the studies have only shown correlations. This does not mean that early puberty necessarily leads to health problems.

“We need further research in this area,” says Professor Petur Benedikt Juliusson in an email to He has led the Growth Study in Bergen.

“It could be worrisome if puberty across the population keeps starting earlier and earlier,” he says.

Head and body out of step

Early puberty can also cause psychological problems, according to a 2014 American study.

The study findings show that girls and boys who reach puberty before their peers have a higher risk of experiencing depression later.

Premature sexual maturation can affect girls’ and boys’ relationship to their own body. They may experience a big difference between how they feel physically and how they feel psychologically, which can lead to mental health issues.

“Through this study, we were able to determine normal puberty development in Norwegian children. That also informs us when development deviates from the norm and when we should follow up with children,” says Bruserud.

Why are girls hitting puberty earlier?

Researchers in Bergen have not yet researched the reasons why girls reach puberty earlier, but they have a few theories.

“The reasons for earlier onset of puberty are probably complex, but the increased incidence of overweight and obesity and chemicals in the environment that can have a hormone-like effect are possible factors,” says Bruserud.

Stress can probably also affect when puberty starts.

Petur Benedikt Juliusson is a professor at UiB’s Department of Clinical Science.

“There is a lot going on in young people’s bodies. It’s not inconceivable that youth are maturing faster both physically and mentally and that this is connected,” she says.

Environmental toxins in makeup may be a cause

Chemical substances – so-called hormone mimics or endocrine disruptors – in makeup and body care products can trigger processes that affect puberty, according to the researchers.

In addition, chemicals and environmental toxins in paints, detergents and plastics can have the same effect. Even parabens in the food we eat can affect children.

The researchers in Bergen, led by Professor Petur Benedikt Juliusson, have received funding to analyse environmental toxins and their effect on young bodies.

“We’ll be starting the project soon, probably during the fall or winter, but it’ll take some time to get the results analysed, probably a couple of years,” says Juliusson.

He will also investigate how genes influence the onset of puberty. The research team will explore epigenetics and look at how our genes change after being influenced by things around us, such as environmental toxins.

Translated by Ingrid P. Nuse


Ingvild Særvold Bruserud m.fl: References for Ultrasound Staging of Breast Maturation, Tanner Breast Staging, Pubic Hair, and Menarche in Norwegian Girls. The Journal of clinical endocrinology & metabolism. March 2020. DOI:


Read the Norwegian version of this article at

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