Girls who start menstruating
at a younger-than-average age do not have sex earlier than their peers,
according to a new study.
found that among 554 girls followed through childhood, those who started their
monthly periods before age 12 did not get an earlier start on their sex lives.
One-quarter had had sexual
intercourse by the time they were 15 years old, versus about 29% of girls who'd
started their menstrual periods at age 12 or 13 which is considered the average
Typically, the study found,
girls who got their first period early waited longer before having sex about
five years versus less than four years among girls who started menstruating at
the average age.
"Our study shows that
earlier physical maturation doesn't necessarily mean that a younger girl will
initiate sexual behaviour," said lead researcher Jennifer Marino, a
research fellow at the University of Melbourne in Australia.
Earlier sex education
Some past studies have
linked earlier menstruation to earlier sexual activity. But, Marino said, those
have generally been of older girls and women who were asked to recall how old
they were when they started their periods and started having sex.
In this study, girls were
followed from childhood to age 20, and they and their parents answered periodic
questionnaires; some girls kept diaries to record their periods.
Still, the findings,
reported online in Paediatrics, do not prove there's no link between
earlier puberty and earlier sexual activity, one expert says.
"The age of menarche
and the age of onset of puberty are not the same thing," said Dr Renee
Boynton-Jarrett, an assistant professor of paediatrics at Boston University
School of Medicine who studies pubertal development.
to a girl's first menstrual period, and that actually happens late in puberty,
Boynton-Jarrett explained. For girls, the first sign of puberty is the
beginning of breast development.
"In the US, the age of
onset of breast development is declining," Boynton-Jarrett noted.
"And it would be interesting to see if the age of pubertal onset is
associated with first sexual activity."
A US study
found that black girls typically start developing breasts at about age 8, while
other girls start at around age 9. The researchers found that among white girls,
breast development is happening sooner now than in the 1990s and a rising rate
of obesity seemed to largely explain the shift.
It's important to
understand whether that earlier development is related to earlier sexual
activity, Boynton-Jarrett said. If it is, she noted, it might be wise to start
sex education in schools a bit sooner.
Race and ethnicity
Another limit of the
current study is that it looked at a group of mostly white girls from Western
Australia, and it's not clear if the findings would extend to more diverse
groups, said Boynton-Jarrett.
Marino agreed. "It's
possible that the US, which has a different racial, ethnic and cultural
composition to Australia, could have different findings," she said. Race
and ethnicity influence the timing of puberty, Marino noted, and a whole host
of factors including family and social influences would affect girls' sexual
But that's also good news
for parents. Even if earlier puberty were to be generally linked to earlier sex,
which would be far from the only factor in any one girl’s odds of becoming
sexually active at a young age, Boynton-Jarrett said.
Regardless of when a child
starts physically maturing, parents should talk to their kids about sex, Marino
"Although some people
think that teaching kids about sex will 'give them ideas', decades of data show
otherwise," Marino said. "Starting conversations early makes it more
likely that teenagers will talk to their parents if they have questions later
on, or find themselves in a tricky situation."
Most of the research on the
timing of puberty and sexual activity has focused on girls. Judging the stages
of puberty in boys is simply more difficult from a practical standpoint, Marino
But, she said, a couple of
small studies involving boys have suggested a link between earlier puberty and
earlier sexual activity.
The American Academy of Paediatrics
has tips on talking to your kids about sex.