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Health and Wellbeing
A Health and Well-being Wales Partner

Puberty refers to the stage in a child’s life when they begin to develop physically and emotionally into young men and women.

It can be a difficult time for children, as they cope with rapid changes in their bodies and deal with unfamiliar feelings and emotions.

Though children may have boyfriends or girlfriends before puberty, this is often the time when they begin to show more interest in romantic and sexual relationships.

Puberty can also be a challenging time for parents and carers, who can sometimes feel that their loving and talkative child has been abducted and replaced by a sullen and non-communicative stranger. Try not to worry – unexplained mood swings are perfectly normal in teenagers and this phase won’t last forever.

Onset of puberty

Thankfully, puberty doesn’t happen all at once. It takes around four years for all the physical changes to take place in a young person’s body.

Most girls begin puberty between 8 and 14, with 11 being the average age.

Most boys begin puberty between 9 and 14, with 12 being the average age.

During this time, their bodies mature gradually and their reproductive organs will become functional. Boys will become taller and more muscular and their voices will become deeper, while girls will start their periods and usually gain some weight. Both sexes may develop acne or body odour (both are more common in boys).

Boys and girls develop at different speeds, with boys often developing later than girls.

For more information about the different stages of puberty visit NHS 111 Wales.

Early puberty

Puberty is occurring earlier in most children than it did a few decades ago; however, when a child shows signs of puberty too early – before the age of 7 or 8 in girls and the age of 9 in boys –  it could indicate a health problem.

Early or precocious puberty affects more girls than boys.

If your child has telltale signs of precocious puberty, it’s always wise to seek advice from your GP who can arrange tests to rule out any medical problem.

Delayed puberty

Children hit puberty at different ages; however, if a boy has shown no sign of reaching puberty at 14 and a girl has not started her periods by 15, they are experiencing delayed puberty.

Delayed puberty can happen for many reasons, including undiagnosed medical problems, long-term conditions and eating orders linked to low body weight in girls.

Delayed puberty is more common in boys and can run in families.

Seek advice from your GP as it’s important to rule out any underlying cause.

Risk-taking behaviour

Puberty is the age when children reach biological maturity; however, reaching puberty does not mean they are now adults, either emotionally or legally. 

The difference between their physical and emotional maturity – and the hormones flooding their bodies – can lead to some young people experimenting with new and potentially risky activities, like sexting, smoking, drinking, drugs or under-age and unprotected sex

Talking to your child

Parents often put off talking to their children about puberty because they find it embarrassing. While this is understandable, young people will find the changes to their bodies and emotions less frightening if they know what to expect beforehand.

Childline has lots of great information about puberty on its website.

The Mix is another good resource for under 25s and includes sections on Sex and Relationships and Your Body.

Last updated: 07/02/2023