Puberty, and the Body That Gets There First

The nine-year-old asks from the back seat on the way home from school, looking out of the window rather than at her mother, whether she can have a crop top like Priya’s. Her mother says of course, in the voice of someone asked whether there can be pasta for supper, and then drives the rest of the way home doing sums. Nine. She was twelve herself, she thinks, or thirteen. She had assumed there were years yet.

Across town, a father notices that his twelve-year-old son has started locking the bathroom door, which the boy never used to do, and that on Sunday, on the phone to his grandmother, the boy’s voice did something halfway through a sentence that made them both laugh, and then made him go silent. Neither child has said a word about their body. Both are telling their parents something.

Parents are often caught out by puberty, because it comes earlier, faster or less visibly than they remember from their own, and the conversations they had planned for twelve are needed at nine.

What is actually happening

Puberty is the set of changes, driven by hormones, that turns a child’s body into an adult one. It usually begins somewhere between eight and fourteen, and takes two to five years from start to finish. On average, girls begin a little earlier than boys: at around eleven for girls and twelve for boys.

For girls, the first sign is usually the beginning of breast development, small and sometimes tender, and sometimes on one side before the other. A growth spurt follows, then pubic and underarm hair, and periods usually arrive about two years after the breasts begin to develop. Most girls start their periods at around twelve, but they can start as early as eight; a first period before ten is worth mentioning to the GP. Early periods are often irregular, and settle over the following few years.

For boys, the first sign is usually that the testicles grow larger, which nobody else notices. Pubic hair follows, then the growth spurt, which in boys tends to come later in puberty than it does in girls, and then the deepening voice, facial hair, erections that arrive without warning, and wet dreams. Many boys have some swelling or tenderness behind the nipples during puberty. It is common, and it usually goes away on its own.

Before any of this, many children of seven or eight begin to smell a little after exercise, and some grow a few hairs under the arms or around the genitals. This is often a separate and earlier process, driven by the adrenal glands, and a normal variation rather than puberty itself. Hair before eight, or before nine in a boy, is still worth showing the GP, who can tell the two apart. Either way, it is a good moment to start the conversations this chapter describes.

### Earlier than it used to be

Parents who remember their own puberty starting at twelve or thirteen are often remembering their first period, which in the UK has changed little in recent decades: in a large UK study of girls born around 2000, about one in ten had started her periods by the age of eleven, much as in 1990. Breast development is a different story. It has been starting earlier: a review of studies from around the world found the average age falling by almost three months a decade between the late 1970s and 2013. Clinics in many countries also saw more children with early puberty during the pandemic years, for reasons that are not yet understood. The causes of the longer trend are still debated, and no single one explains it.

### Early, and late

The NHS describes signs of puberty before the age of eight as possibly early, and no signs by fifteen as possibly delayed. Specialists use slightly different ages for girls and boys. For a girl, no breast development by thirteen, or no period by fifteen, is late, and the NHS page on periods agrees. For a boy, signs before nine count as early, and none by fourteen as late. Any of these is worth a visit to the GP. Most of the time there is nothing to worry about, and treatment is usually needed only if early or late puberty is causing physical or emotional problems.

What is happening in her head

The hormones of puberty are only part of the story. Adolescence brings a reorganisation of the brain that carries on well into the twenties, and some of the changes most visible at home are social ones. Young teenagers become more sensitive to what their friends think, more affected by being left out, and more self-conscious, with a strong sense of being watched. Research led by the neuroscientist Sarah-Jayne Blakemore has traced how this social side of the brain develops in adolescence, and has found early signs that puberty itself plays a part. Two cautions are worth holding on to. Averages hide enormous differences between one young person and the next, and the popular idea that the teenage brain is broken is not what the science shows.

Mood often shifts. Children describe feeling things more strongly, crying more easily, or being irritable for reasons they cannot name. Childline tells young people that mood swings are a normal part of puberty, and that they may feel happy one minute and irritable, grumpy or tearful the next. We would add that “moody” is a word best not used in front of them.

Sleep changes too. As puberty advances, the body clock shifts later, so that a teenager is less sleepy at ten at night and much sleepier at seven in the morning. Her need for sleep does not fall; the Royal College of Psychiatrists puts it at nine to ten hours. The teenager who cannot get up is running on a different clock, and the library’s chapter The Hour Before Bed has more on helping her.

And sexual feelings begin. Crushes, curiosity and, for many, masturbation are a normal and private part of puberty. What she needs from you is a sense that her body is hers, that her feelings are normal, and that she can ask you questions without being laughed at.

When it comes early

Most early developers do perfectly well. But early puberty is linked with a small extra risk, in girls and in boys, of anxiety, low mood, eating difficulties, behaviour problems and drug or alcohol use; a review of more than a hundred studies found the effect consistent and small. In a UK study that has followed children from birth, girls whose periods started early had more symptoms of depression at fourteen, and the difference had faded by their mid-twenties. A separate study of the boys in that group found that those who matured early were more likely to be depressed at eighteen.

Some of the reasons are easy to see. A nine-year-old with a changing body is not ready for the comments it can attract, and early-developing girls in particular can draw attention from older boys and adults, and drift towards older friends. Two things appear to protect her. The first is feeling prepared: in one American study of university students, young women who remembered feeling unprepared for puberty, and disliking its changes, had more symptoms of disordered eating, and those memories mattered more than their background or their present circumstances. The second is feeling accepted at home.

So if your child is developing early, the job is to protect her without policing her. Prepare her before the changes come, so that none of them is a shock. Talk to her about comments, from other children and from adults, and about what she can do with them. Keep an eye on who she is spending time with, online and off, without treating her new body as a problem. Never comment on her shape or her weight. And if anyone remarks on her body in front of you, deal with it calmly, and on her side.

For boys who develop late, the difficulty is the opposite: the changing room, being the smallest in the year, the voice that has not broken. The same principle applies. Prepare him, tell him how wide the normal range is, and see the GP if nothing has started by fourteen.

The conversations

Start before it starts. By seven or eight, most children are ready for the basic facts: that bodies change as they grow up, roughly how, and that this happens to everyone. The NHS advises treating periods as an ongoing conversation rather than a formal sit-down talk, and that matches our experience of puberty generally. One big talk at eleven is too late for some children and too much for most. Many small conversations from seven onwards, in the car, over the washing-up, prompted by an advert or a book, make puberty ordinary.

Use the right words. The NSPCC encourages parents to use the correct names for body parts if they are comfortable doing so. Children who know the words can ask questions, describe pain, and tell an adult if something is wrong.

Leave a good book lying around. Many children prefer to read about it on their own first and ask questions afterwards. There are suggestions at the end of this chapter.

Answer what is asked. Truthfully, at her level, and without a lecture. “That’s a really good question. I’m not sure how to explain it well, so let me think about it and come back to you tonight” is a perfectly good answer, as long as you do come back.

Not only mothers and daughters. Boys need to know about periods, and girls about boys’ puberty; it makes them kinder to each other, and less frightened of what they half-know. Fathers and other male carers matter here. Girls in one study said they wanted their fathers to be supportive about periods without making a big thing of it. In practice that means knowing the facts, buying pads without comment, and never making a joke at her expense.

Privacy and dignity. Knock before going into her room or the bathroom. Let her decide who is told about her first period: it is hers to share, not news for the grandparents. Make teasing about bodies, by brothers and sisters as much as by anyone, something the family does not do.

Be practical. Before her periods are likely to start, put together a small kit for her school bag: pads, a spare pair of pants, wipes and a small bag to keep them in. Show her how pads work, and let her decide in her own time about tampons or period pants; there is no right age. For boys, deodorant, a razor when he wants one, and a matter-of-fact word that erections and wet dreams are normal and nothing to be embarrassed about. Find out how the school handles periods: the government scheme that provides free period products covers state schools in England but not independent schools, so ask the school what is in place.

What school teaches, in England

Statutory guidance on relationships, sex and health education, in force in England since September 2026, sets no minimum age for teaching about puberty, and says that periods should be covered before girls’ periods start, recognising that they can start at eight. In state schools, primary pupils learn the correct names of body parts, and secondary pupils learn about heavy periods, endometriosis and polycystic ovary syndrome.

For independent schools the rules are a little different. Relationships education and relationships and sex education are compulsory for them, but health education, where puberty sits, is not, though independent schools must teach personal, social, health and economic education (PSHE). Each independent school decides for itself how and when to teach puberty, so ask your child’s school what it covers and when, and get there first. In any school in England, parents can ask for a child to be withdrawn from sex education, but not from relationships education. In state schools, they cannot withdraw a child from health education, or from the puberty content of science lessons; whether an independent school allows withdrawal from parts of PSHE is a matter for its own policy. The rules in Wales, Scotland and Northern Ireland are different again.

Periods that need a doctor

Some period pain is common, and early periods can feel heavy. But periods should not stop a girl living her life, and if they do, it is worth seeing the GP. The NHS describes heavy periods as needing to change a pad every one to two hours or to use two products at once, bleeding for more than seven days, passing clots larger than about 2.5 centimetres (the size of a 10p coin), bleeding through clothes or bedding, or feeling tired or short of breath a lot. If she has had heavy periods from the start, and she bruises or bleeds easily or there is a family history of bleeding problems, mention that as well, because doctors may test for a clotting disorder.

Pain that stops her doing her usual things deserves a GP appointment. Pain that is severe or worse than usual, and not helped by painkillers, deserves an urgent appointment or a call to 111 (in Northern Ireland, the GP out-of-hours service). NICE tells doctors to suspect endometriosis in girls under eighteen whose period pain affects their daily life, and to ask whether their mother or sister has it. In the UK, a diagnosis of endometriosis takes more than nine years on average. Take her pain seriously, and if you are not satisfied, go back and say so.

When puberty is hard for other reasons

Body image and eating. Puberty changes the body’s shape, and often arrives alongside a sharper awareness of how bodies are judged. If she starts dieting, skipping meals, exercising compulsively or talking about her body with disgust, read the library’s chapters Body Image and Eating and Control, and see your GP.

Low mood. The early teenage years are when low mood becomes more common, especially in girls. The library’s chapter When Your Child Has Gone Flat covers what to look for.

Questions about gender. Some children find the arrival of puberty distressing because of questions about their gender. If that is your child, listen without deciding anything on their behalf, and keep the conversation open. Talk to your GP, who can refer to local children’s mental health services or to a paediatrician; in England, only those services, not the GP, can refer on to the NHS children’s gender service, where the waits are long. Medicines that pause puberty are not started for gender distress in under-eighteens in the UK, other than within a research trial. The library’s chapter When Your Child Is Working Out Who They Are goes into this more fully.

When something is wrong. Sometimes sexual knowledge in a young child, or sexual behaviour well beyond her age, is a sign that someone has shown her sexual material or harmed her. If you are worried, talk to her school’s designated safeguarding lead, or to the NSPCC helpline, which gives advice to any adult concerned about a child. If you think she is in immediate danger, call 999. If the person you are worried about lives with her, in your home or another, go straight to children’s social care or the police.

At different ages

The bands below are descriptions, not boxes.

If your child is between seven and nine. This is the time to start. Read a book together, use the right words, and treat the occasional question as an opening, not an emergency. A little body odour at this age is usually nothing more than that. Hair under the arms or around the genitals, breast development, or changes to the genitals before eight, or before nine in a boy, are worth showing the GP. Children of this age tend to be more curious than embarrassed, which makes it the easiest time to talk.

If your child is between nine and eleven. For many girls, puberty begins here, and for some, so do periods. Put the kit in the school bag before it is needed. Find out when the school’s puberty lessons happen, and talk to her before they do, so that school confirms what she already knows. Most boys will not have started yet, but they need the same information, about their own bodies and about girls’. Changing rooms, sleepovers and swimming lessons can suddenly become difficult; ask, and make room for privacy.

If your child is in early secondary, eleven to thirteen. Most girls are in the middle of puberty, and most boys are starting it. Self-consciousness is at its height, and so is comparison with friends, much of it now happening on phones. Expect more time behind a closed door, and a body clock that runs later. This is a good age to talk about sexual feelings, consent and the pressures of the group chat; the library’s quick tips The Talk Before It Is Needed and Before Someone Shows Her Porn can help.

If your child is mid-teen, thirteen to sixteen. For many girls puberty is largely complete, and for many boys it is in full flow. Late developers, more often boys, may need reassurance, and a visit to the GP if a girl has no breast development by thirteen or no period by fifteen, or a boy no signs by fourteen. She should now be managing her own periods, with you in the background; if they are heavy or painful, help her get them taken seriously.

Your own puberty

Most parents of today’s children grew up with very little said about any of this. Some remember a leaflet, a single excruciating conversation, a first period on a school trip, a nickname that stuck. Those memories travel with us, and they shape what we say, or do not say, to our own children. It is worth noticing them, so that they do not steer the conversation. You do not have to be perfectly comfortable to talk about puberty well. You only have to be someone she can ask.

The longer arc

Puberty takes a few years, and then it is done. What lasts is what she learned about her body along the way: whether it was something to be ashamed of or something she understood, whether questions were welcome, and whether the adults around her could talk about bodies without embarrassment or judgement. In our experience, a child who could ask you about periods at nine finds it easier to come to you about harder things at fifteen.

The nine-year-old in the back of the car will have her crop top by the weekend. It might come with a book left on her bed, a sentence or two in the car the following week, and a growing sense that this is something the two of them can talk about.

NOTES

1. NHS. “Early or delayed puberty.” Reviewed 2026. Puberty usually starting between eight and fourteen; signs before eight as possibly early and none by fifteen as possibly delayed; treatment usually needed only if early or late puberty is causing problems.
2. nidirect. “Early or delayed puberty.” Scottish Paediatric Endocrine Network (SPEG). Guideline for Investigation of Early (Precocious) and Late (Delayed) Puberty in Girls and Boys. NHS National Services Scotland, 2024. Average ages of onset; the usual order of changes; puberty taking two to five years; early body odour and hair as a possible normal variant; delay as no breast development by thirteen in girls and no testicular growth by fourteen in boys; early onset in boys as before nine; referral for a first period before ten.
3. NHS. “Starting your periods.” The average age of twelve and the earliest of eight; periods arriving about two years after breast development begins; seeing a GP if periods have not started by fifteen, or thirteen with no other signs; talking about periods as an ongoing process; boys learning about periods too. NHS. “Gynaecomastia.”
4. Kelly, Y., Zilanawala, A., Sacker, A., Hiatt, R. and Viner, R. “Early puberty in 11-year-old girls: Millennium Cohort Study findings.” Archives of Disease in Childhood, 2017. Eckert-Lind, C. et al. “Worldwide secular trends in age at pubertal onset assessed by breast development among girls: a systematic review and meta-analysis.” JAMA Pediatrics, 2020. Nguyen, N. N., Do, T. D., Truong, H. H., Mai, A. N. and Chen, Y.-C. “Difference in precocious puberty between pre-COVID-19 and COVID-19 periods: a meta-analysis.” American Journal of Epidemiology, 2025.
5. Andrews, J. L., Ahmed, S. P. and Blakemore, S.-J. “Navigating the social environment in adolescence: the role of social brain development.” Biological Psychiatry, 2021. Blakemore, S.-J., Burnett, S. and Dahl, R. E. “The role of puberty in the developing adolescent brain.” Human Brain Mapping, 2010. Foulkes, L. and Blakemore, S.-J. “Studying individual differences in human adolescent brain development.” Nature Neuroscience, 2018.
6. Childline. “Top facts about puberty.” Carskadon, M. A. “Sleep in adolescents: the perfect storm.” Pediatric Clinics of North America, 2011. Royal College of Psychiatrists. Sleep Problems: For Parents and Carers.
7. Ullsperger, J. M. and Nikolas, M. A. “A meta-analytic review of the association between pubertal timing and psychopathology in adolescence: are there sex differences in risk?” Psychological Bulletin, 2017. Prince, C., Joinson, C., Kwong, A. S. F., Fraser, A. and Heron, J. “The relationship between timing of onset of menarche and depressive symptoms from adolescence to adulthood.” Epidemiology and Psychiatric Sciences, 2023. Tarif, D., Heron, J., Fraser, A., Elhakeem, A. and Joinson, C. “Pubertal timing, depressive symptoms, and depression in adolescent males: a prospective cohort study.” Psychological Medicine, 2025.
8. Mendle, J., Turkheimer, E. and Emery, R. E. “Detrimental psychological outcomes associated with early pubertal timing in adolescent girls.” Developmental Review, 2007. Moore, S. R., McKone, K. M. P. and Mendle, J. “Recollections of puberty and disordered eating in young women.” Journal of Adolescence, 2016. Benoit, A., Lacourse, E. and Claes, M. “Pubertal timing and depressive symptoms in late adolescence: the moderating role of individual, peer, and parental factors.” Development and Psychopathology, 2013.
9. NSPCC. Talk PANTS: A Guide for Parents. 2023. Koff, E. and Rierdan, J. “Preparing girls for menstruation: recommendations from adolescent girls.” Adolescence, 1995.
10. Department for Education. Period Product Scheme for Schools and Colleges. Updated 2026.
11. Department for Education. Relationships Education, Relationships and Sex Education (RSE) and Health Education: Statutory Guidance. Published July 2025, in force from 1 September 2026, paragraphs 2, 16 and 21 and footnote 4. No age limit on teaching puberty; periods taught before they start; correct names of body parts in primary health education; the position of independent schools; parents’ rights to request withdrawal.
12. NHS. “Heavy periods” and “Period pain.” NICE. Heavy Menstrual Bleeding: Assessment and Management (NG88), 1.2.7. NICE. Endometriosis: Diagnosis and Management (NG73), 1.3.1 and 1.3.2. Endometriosis UK. The State of Endometriosis Care in the UK. 2026.
13. Department of Health and Social Care. “Ban on puberty blockers to be made indefinite on experts’ advice.” 11 December 2024. NHS England. Service Specification: National Referral Support Service for Specialist Service for Children and Young People with Gender Incongruence. 2024.
14. NHS. “Testicle pain.” 2025. NCEPOD. Twist and Shout: A Review of the Pathway and Quality of Care Provided to Children and Young People Aged 2 to 24 Years with Testicular Torsion. 2024. When to go to A&E, and the six-hour window.

Where to go further

Sarah-Jayne Blakemore, Inventing Ourselves: The Secret Life of the Teenage Brain A leading neuroscientist of adolescence on what is happening in the teenage brain, written for a general reader. It makes the closed door and the late mornings easier to understand, and harder to take personally.

Anna Claybourne, Don’t Panic, It’s Puberty! A Guide for Girls, and Tim Collins, Don’t Panic, It’s Puberty! A Guide for Boys Two short, matter-of-fact guides for children of about eight and over. Worth having both in the house, whichever child you have.

Yumi Stynes and Dr Melissa Kang, Welcome to Your Period A warm, frank and funny book for girls of about ten and over, with the practical detail they actually ask for.