During puberty, the body becomes capable of reproduction. For girls, this means the onset of menstruation (periods) – the monthly shedding of the uterine lining. Menarche (first period) typically occurs around age 12–1311, though it can range from 10 to 15. Early cycles are often irregular and light at first. For boys, puberty brings sperm production. The first ejaculation (“spermarche”) usually occurs around ages 12–1512. Boys may notice wet dreams (nighttime ejaculation) as a sign of fertility starting. Both processes are normal and mean the body is developing normally.
Menstruation and Sperm Production
What It Is
Why It Matters
Understanding these changes is crucial for health and confidence. A girl who knows what menstruation is will feel prepared (and less scared) when it begins. Good menstrual hygiene (changing pads/tampons regularly, washing) prevents infections and makes periods more comfortable. For boys, normalizing erections, wet dreams, and producing semen helps them feel less embarrassed. Recognizing fertility changes also ties into learning about reproduction (important later for pregnancy prevention). Overall, knowledge about menstruation and sperm empowers teens to take care of their bodies and respect others going through the same changes.
Statistics to Know
- Menarche age: On average, girls have their first period at about 12.4 years11, often about 2 years after initial breast development.
- Menstrual pain: Up to 80–85% of teen girls report menstrual cramps (dysmenorrhea) at some point (often mild)13. A smaller portion (~5–10%) have severe pain affecting activities.
- Spermarche age: Research shows first ejaculation typically occurs between 12 and 15 years old12. (This matches menarche age in many countries.)
- Adolescent fertility: By age 18, most adolescents have gone through these changes: in the U.S., about 90% of girls have had menarche by age 15 (CDC data) and over 90% of boys have spermarche by age 16.
Age-Specific Guidance
Ages 9-12
For girls, begin talking about periods before they happen – often around age 10. Explain that a little bleeding from the vagina will start and is normal. Teach pad/tampon use (changing every 3–4 hours) and carrying supplies in a backpack. Stress cleanliness: wash hands before and after changing. For boys, explain erections (morning wood, spontaneous erections) as normal; these will be common and should just be ignored or handled privately. Mention that wet dreams are a normal way sperm comes out once puberty is underway. Encourage both sexes to ask questions about body changes. Use correct terms (vagina, penis, uterus, sperm) so they learn respectfully.
Ages 13-18
Girls’ periods usually settle into a regular cycle (every 28±7 days) by mid-teens. Talk about common symptoms (bloating, mood swings) and relief (heating pad, exercise, medication if needed). Emphasize hygiene (shower often, change products). For boys, discuss genital hygiene: washing daily, using loose cotton underwear to stay dry. If concerned, show them how to check for any lumps (self-awareness, though routine doctors’ checks are standard). If shaving body hair (underarms, chest, pubic area), teach safe shaving to avoid cuts. Encourage teens to see a healthcare provider if they have very heavy periods (soaking overnight) or painful erections/persistent discomfort (so they learn it’s normal but also safe to ask a doctor about big problems).
Common Questions Parents Have
Q: “When will I get my first period (or have sperm)?”
A: Each body is unique. Most girls start between ages 10–15 (often around 12–13)11. If you haven’t by 16, a doctor visit can check that your body is developing normally. Boys usually experience their first ejaculation between 12–1512. Both can happen earlier or later; ask a pediatrician if you’re worried.
Q: “My friend’s period started and mine hasn’t – is something wrong?”
A: No. Periods and sperm production follow different timelines. One friend might start earlier or later. It often depends on genetics, health and nutrition. Encourage patience: describe how most changes begin over several years. If a teen girl still hasn’t started by age 15, she should see a doctor to rule out any issues. Otherwise, normal.
Q: “What can I do about cramps or breast pain?”
A: Many girls have mild cramps or tender breasts around their period, especially early on. Light exercise, warm showers, and over-the-counter pain relievers (ibuprofen, acetaminophen) can help. Wearing a supportive bra (for girls) can also ease breast discomfort. If cramps are severe (making you faint or forcing you to miss school), tell a parent and doctor – there are treatments available.
Q: “Is it normal for boys to get erections at random times?”
A: Yes. Boys can get erections for many reasons – hormone changes in puberty mean the blood flow to the penis can increase spontaneously. It might feel embarrassing, but it’s a normal sign the body is working. If it happens, just relax or discreetly shift focus (like thinking of something else). Over time, as you grow older, it happens less frequently.
Q: “How often should I change pads or tampons?”
A: As often as needed. A general rule is every 3–4 hours, or whenever the pad/tampon feels wet. This keeps you clean and prevents leaks or odors. Remind your child to carry extra products in their backpack. For boys: it’s good to shower daily and wash with mild soap after sweating a lot or after sports.
Recommended Resources
- A Mighty Girl - Teaching Your Mighty Girl About Her Menstrual Cycle - Books and resources for preparing girls for their first periods.
- The Period Book: A Girl's Guide to Growing Up by Karen Gravelle - A comprehensive guide to understanding periods.
- KidsHealth - Menstruation - Information for teens about menstruation.
- Young Men’s Health - Puberty for Boys - Information about male puberty, including sperm production.