Puberty & how bodies work

Lesson 1

Everyone’s timeline is different

Puberty is when your body starts changing from a child’s body into an adult’s. It usually starts between ages 8 and 13 for girls and between 9 and 14 for boys, according to the National Institutes of Health. Starting earlier or later than your friends is common.

• For girls, the first sign is usually breast buds, small bumps under the nipples. For some girls, pubic hair comes first.
• For boys, the first sign is usually growth of the testicles and scrotum.
• For everyone: a growth spurt, new body hair, and often acne.

It’s worth checking in with a clinician if a girl has no changes by 13 or a boy has none by 14, or if changes start before 8 for girls or 9 for boys.

Lesson 2

Periods

Most people get their first period around age 12, and anywhere from 8 to 15 is normal. It usually comes about 2 years after breasts start to develop.

• How long: a period lasts about 5 days on average, usually 2 to 7.
• How often: for teens, anywhere from 21 to 45 days from the start of one period to the start of the next. Cycles are often irregular for the first few years.

Lesson 3

Changes for boys

• Erections can happen for no reason at all. That’s normal, and they happen less often over time.
• Wet dreams, releasing semen during sleep, are normal and nothing to be ashamed of. They usually start between 13 and 17.
• Breast swelling happens to at least 3 in 4 boys and usually goes away within 1 to 2 years.
• Your voice may crack for a while, then settles once your voice box reaches its adult size.
• Facial hair usually comes about 2 years after pubic hair.

Lesson 4

How pregnancy happens

A pregnancy starts when a sperm meets an egg in the fallopian tube. The fertilized egg travels for a few days, then implants in the wall of the uterus.

An egg lives for about 12 to 24 hours after it’s released, but sperm can live inside the body for up to 5 days. So there are about six days in each cycle when sex can lead to a pregnancy, and because teen cycles are often irregular, it’s hard to know when those days are.

Waiting is the only sure way to prevent a pregnancy.

Lesson 5

Feelings, questions and care

Many people notice stronger emotions and new feelings during puberty. That’s part of growing up, and no question about your body is too embarrassing to ask.

• Talk it through with a parent, a trusted adult or your doctor.
• Get the HPV vaccine. The CDC recommends it at age 11 or 12, and it can start at 9, to protect against cancers caused by HPV later in life.
• Take care of the basics: sleep, food and movement all help your body through these changes.

Check yourself

Myth or fact?

Questions people ask

Asked and answered.