March 19, 2002
You may have noticed that young girls seem to be maturing at a younger age and studies have confirmed it. But as Peta Newbold reports early puberty in girls has important clinical, educational, and social implications.
Jennifer was astonished when her daughter's 10-year old friend had a period during a 'sleepover' party at her home. It wasn't her first one either. "It was a real wake up call for me," she said. "I hadn't really discussed sexuality with my daughter before, not because I have a problem with it, rather because it never occurred to me. However when I talked to other parents it was common knowledge that a few other girls in the class had hit puberty too."
Landmark US study
The anecdotal evidence that girls are sexually maturing earlier was confirmed in a study involving 17,000 American girls published in the Journal 'Pediatrics' in 1997. The results varied depending on ethnic background but the average age of onset for girls was a year or a year and a half younger than previous research had shown.
On the average, a white girl now begins breast development around her tenth birthday, and the African American girl around eight years and nine months.
It showed that white girls start to grow pubic hair at about ten and a half and African American girls at about eight years and seven or eight months.
However the study didn't find that menstruation started earlier in that same population of girls, with the exception of the African-American girls. The age of what's known as menarche or first period for Caucasian girls was 12.8 years; for African-Americans, it was about six months earlier.
The picture in Australia
According to Dr Terri Foran Medical Director of FPA Health there are no similar studies involving Australian girls but she says that information on the menarche has been collected throughout the 20th Century. In 1900 the average age was 17 and it has fallen to 12.5 in Australia where it has remained steady for the last decade.
Why are girls growing up fast?
Talk to many Australian parents and they'll blame the falling age of puberty on growth hormones in chickens. However the Chief Executive of the Australian Food and Grocery Council, Mitchell Hooke put that claim firmly to bed in the Sydney Morning Herald last year. "We haven't fed growth hormones to chickens for 30 years, but you still get a number of seriously educated people who say that is what brings on early puberty and mammary growth in girls," he said.
The importance of Body Mass Index
So why are girls growing up so fast? A follow up U.S. study in 2001 confirmed what many had already suspected, that obesity was an important contributing factor.
Body Mass Index (BMI) is a guideline based on weight and height to determine whether a person is under or overweight and there is now even further evidence that it influences puberty. Professor Michael Bennett of the School of Women's and Children's Health at the University of New South Wales reported that there has been a recent upturn in the age of the menarche in the United Kingdom, Iceland, Poland Italy and Sweden. He says that although the reasons are not clear it's thought that an increase in exercise and the desire to be slim may be factors.
Clearly BMI is only part of the picture though and experts suggest that a number of other factors may be at play depending on the individual and her circumstances:
- Pheromones Girls may be exposed to pheromones, or sexual hormones, from unrelated men such as stepfathers, prompting them to sexual development.
- Chemicals Some studies have indicated an association between exposure to certain chemicals called phthalates which act as a softener causing plastic to become flexible, and early breast development.
- Stress Another theory is that children who live in families without fathers may be experiencing stress, bringing about early puberty.
- Sex and TV The suggestion is that an increase in images of sex on television may foster sexual maturity, in a way that food stimulates salivation.
There are many unanswered questions on early puberty besides 'what's causing it?' Is it continuing to decline? is another and no one yet knows. In the meantime girls who mature early raise some interesting issues for schools, GPs, health policy makers and parents.
Is my daughter normal?
If the average girl has her first period at age 12.5 it means there is a younger end of normal that is around 9 or 10 and an upper end of about 14 or so. Even so according to Dr Foran, it is unlikely that girls having their first period beyond those norms would be investigated unless there were other health issues involved.
However she warned, "It is the girls on the far ends of the spectrum who have the hardest time. The first period is always accompanied by a growth spurt so you get girls at the lower end who are bigger than their classmates, who are squeezed into dresses with no room for breasts, who find there are no sanitary products in the toilets and where touch games are no longer appropriate.
At the other end of the spectrum there is the 15 year-old who is always at the front of the school photograph because she's the smallest and she has boys poking at her and teasing her about her lack of breast development. These girls are not catered for," she said.
"This is a serious public health issue," according one of the authors of the original 1997 landmark study. Professor Marcia Herman-Giddens of the University of North Carolina School of Public Health said, "We don't know about the sexual urges of 7 and 8 year-old girls and how they might affect their mental health."
The clinical implications of early puberty may also be serious because early menarche, like late menopause are among the few risk factors for breast cancer that have been firmly established. However it should be said that it is only one of the risk factors involved.
It has been suggested that if these girls do not become aware of their blossoming sexuality, they might become victims of sexual predators. Dr Foran said, "Parents have to be franker about sex from early childhood to give their daughters self respect and the knowledge to protect themselves from predatory people."
She suggests that sex education should begin at home where a child can become familiar with sexual terms without embarrassment. At school sex education has to be carried out in an environment which encourages children to not to see sex as something smutty, and conversations between the sexes should be encouraged so they can find out from each other what growing up is like for each of them.
"It has to be done in a day to day setting and be part of a continuum. It should be a seamless mix with everything else that's going on in kids lives," she said.
And what of boys?
Whether boys are experiencing early puberty is unknown. Research is ongoing.
1997 Early on set of puberty study. PEDIATRICS Vol. 99 No. 4 April 1997, pp. 505-512)
2001 study on obesity and early onset of puberty. PEDIATRICS Vol. 108(2) Aug 2001; pp. 347-53
FPA Health at http://www.fpahealth.org.au/
ABC News at http://abcnews.go.com/sections/living/DailyNews/earlypuberty010207.html
By Peta Newbold
Reprinted with permission from Editforce