Girls and Puberty

Medically Reviewed by Amita Shroff, MD on August 28, 2022
5 min read

Girls, see if this sounds familiar. You look in a mirror one morning and notice you're taller -- and rounder. Through your nightgown, you see your breasts are bigger. You don't remember looking like that a few weeks ago! Over the next few weeks, you start noticing hair in places you've never had hair before. You've heard girls at school talk about getting their periods, and you wonder if that will happen to you soon. You feel ultraconfident, and then super sensitive -- all in the same day. What in the world is going on? Welcome to puberty.

Technically speaking, puberty is nature's way of transforming a child into an adult, all for the sake of reproduction. While both girls and boys go through puberty, girls reach puberty and sexual maturity at earlier ages than boys do.

So what's causing all of these changes? Hormones! Actually, the female hormone estrogen is the main one that's triggering all the changes in your body. Let's look at some of the changes girls can expect at puberty.

Starting at around age 9, girls begin to gain about 17% to 18% of their adult height. If someone has commented that you are "all hands and feet," it's true! Your limbs grow first, then your trunk. Most girls grow fastest about six months before they start their first period (menarche).

You'll probably gain weight in puberty -- most girls do. You may notice more body fat along the upper arms, thighs, and upper back. Your hips will grow rounder and wider; your waist will become narrower.

Your doctor will check your height and weight each year to make sure you are growing properly. If you are gaining weight too fast, you may need to increase your exercise and substitute fruits and vegetables for junk foods.

Breast development is an early sign of puberty in girls. This can happen before age 9 in some girls, but later in others.

If you are self-conscious, you might want to start wearing a "training bra," which is a soft bra with no real support.

Talk to your mom, older sister, an aunt, or any female you feel comfortable discussing such topics with about buying a training bra. They can help you to make sure you get one that is comfortable and that lets you feel confident in your clothes.

While for most girls, breast development is the first sign of puberty, others might first notice pubic hair. An increase in hair on your arms and legs, in your armpits, and around your pubic area happens to girls early in puberty.

If you want to shave your legs and underarms, ask your mom or another woman you trust about selecting the safest razor. Someone who is experienced in shaving needs to show you how to shave safely; using a gentle shaving cream, water, and a razor. There are other methods of hair removal that you and a trusted adult can explore too.

Keep in mind that not all women shave their body hair. In some cultures, it is acceptable to leave the armpits and legs unshaven. You have to decide what is best for you and your family's customs.

Soon after they develop breasts, most girls have their first menstrual period. Most girls get their first period when they're between 10 and 15 years old. The average age is 12, but every girl's body has its own schedule.for menstruation and it can start earlier or later. During a menstrual period, there are two to three days of heavier bleeding with two to four days of lighter flow.

Menstruation happens to all girls. It's part  of the reproductive cycle, so try not to be embarrassed in learning more about it. Talk to your mom or an adult you trust about having your period.

During your period, you'll need to wear a sanitary pad or tampon. Your mom (or other adult) can purchase these products and show you how to use them. Be sure to keep extra pads or tampons in your school locker in case your period starts suddenly during the school day. If you forget, ask to see a school nurse or ask a female teacher for help.

Cramps are caused by the increased production of hormones during your period. This causes the muscles of the uterus to contract. You might also notice:

Medications such as acetaminophen (Tylenol) , ibuprofen (Advil) and naprosyn (Aleve) can help ease period pain. Putting a heating pad or hot water bottle on your abdomen may also help. If your cramping is severe, talk to your health care provider.

Because of the surges in hormones during puberty, many girls feel moodiness at times, especially right before their periods. This is called premenstrual syndrome (PMS). PMS may cause:

  • Irritability
  • Difficulty sleeping
  • Fluid retention
  • Anxiety
  • Dietary cravings

Once your period starts, the PMS symptoms usually disappear. It's helpful to exercise during PMS and your period in order to boost your mood and help you feel your best. If your mood is lower than normal, talk to your health care provider about your feelings.

Some girls have a decrease in self-esteem and body satisfaction if they hit puberty earlier than their friends. Other girls feel different if they enter puberty later than their friends do. That's why it's important to understand what's happening to your body, and realize that every girl goes through the same changes -- some sooner, some later. But if you have not gone through puberty by age 14, including menstruating, you should see your health care provider.

It's important to eat a balanced diet, exercise daily, get plenty of sleep, and stay at a healthy weight during this time. Continue to see your primary health care provider for regular checkups, so you can feel your best and have someone knowledgeable to go to with your questions or concerns.