Your Changing Body: Puberty in Girls
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Puberty is the time when your body changes and becomes more like an adult.
It is normal for changes to start as early as 8 years old or as late as 13 years old. Puberty starts when your brain sends signals to certain parts of the body to start growing and changing. These signals are called hormones. Hormones are chemicals that control body functions.
During puberty, hormones cause the following changes:
As your breasts start to change, the darker areas around the nipples (called the areolas) may look swollen. The breasts also grow rounder and fuller. One breast may seem a little larger than the other. They may feel sore at times. This is all normal.
Beginning in puberty, every month your body will prepare for a possible pregnancy. Hormones signal the ovaries to release an egg each month. The egg moves into one of the fallopian tubes. At the same time, the lining of the uterus begins to grow and thicken. If the egg is not fertilized by a man’s sperm, pregnancy does not occur. The lining breaks down and flows out of the body through the vagina. This is called menstruation, the menstrual period, or just your “period.”
Most girls in the United States start between the ages of 12 years and 14 years, but some start earlier or later.
Periods usually last between 2 days and 7 days. They normally come every 21–45 days. They often are not regular at first. You may miss a period. You may have two periods in 1 month. This is normal. It can take about 1-2 years after your first period for your body to get on a regular cycle. Keep in mind that if you have had sexual intercourse, a missed period can be a sign that you are pregnant.
It is best to be prepared for your period, even if you have not started yet. Have pads, tampons, or a menstrual cup ready at home and carry them with you to school.
Pads attach to the inside of your underwear. They absorb the blood as it leaves the vagina. Tampons are inserted into the vagina. They catch the blood before it leaves the body. Menstrual cups collect menstrual flow rather than absorbing it the way pads and tampons do.
You should change your pad or tampon at least every 4–8 hours. On the first days of your period, you may need to change it more often because your flow may be heavier. If you use a menstrual cup, you should empty, wash, and reinsert it at least 2 times per day.
Some girls have cramps (tightness and pain) in the lower abdomen and back at the start of their periods. Some girls get headaches or feel dizzy. Some get diarrhea.
To help ease cramps, you can try the following:
- Take ibuprofen or naproxen sodium (if you do not have an allergy to aspirin or severe asthma).
- Place a heating pad on your abdomen or lower back.
Talk to your doctor or your parents about your period for any of these reasons:
- You are 15 years old and have not had a period.
- Your periods were regular each month and then they stopped being regular.
- Your period comes more often than every 21 days or less often than every 45 days.
- Your periods come 90 days apart (even if that happens only once).
- Your periods last more than 7 days.
- Your periods are so heavy that you have to change pads or tampons often (more than once every 1–2 hours).
- You have bad cramps that keep you from doing your regular activities and they are not helped by pain relievers.
An obstetrician-gynecologist (ob-gyn) is a doctor who specializes in the health care of women. Girls should have their first gynecologic visit between the ages of 13 years and 15 years. The first visit may be just a talk between you and your doctor. You can find out what to expect at future visits and get information about how to stay healthy. You can ask questions about your body, growing up, and sex.
Acne is caused by overactive glands in the skin. They make a natural oil called sebum. During puberty, these glands make extra sebum that can clog the pores in your skin.
Wash your face often with water and mild cleanser to help get rid of the extra sebum. This will help reduce pimples and acne. Avoid products that dry or irritate your skin. Do not scrub or pick at your skin. If you have concerns about acne or pimples, some medications can help. Talk to your doctor about your concerns.
Egg: The female reproductive cell made in and released from the ovaries. Also called the ovum.
Fallopian Tubes: Tubes through which an egg travels from the ovary to the uterus.
Hormones: Substances made in the body that control the function of cells or organs.
Menstruation: The monthly shedding of blood and tissue from the uterus that happens when a woman is not pregnant.
Obstetrician–Gynecologist (Ob-Gyn): A doctor with special training and education in women’s health.
Ovaries: The organs in women that contain the eggs necessary to get pregnant and make important hormones, such as estrogen, progesterone, and testosterone.
Puberty: The stage of life when the reproductive organs start to function and other sex features develop. For women, this is the time when menstrual periods start and the breasts develop.
Sexual Intercourse: The act of the penis of the male entering the vagina of the female. Also called “having sex” or “making love.”
Sperm: A cell made in the male testes that can fertilize a female egg.
Uterus: A muscular organ in the female pelvis. During pregnancy this organ holds and nourishes the fetus.
Vagina: A tube-like structure surrounded by muscles. The vagina leads from the uterus to the outside of the body.
Vulva: The external female genital area.
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If you have further questions, contact your ob-gyn.
Published: December 2018
Last reviewed: December 2018
Copyright 2020 by the American College of Obstetricians and Gynecologists. Read copyright and permissions information.
This information is designed as an educational aid to patients and sets forth current information and opinions related to women’s health. It is not intended as a statement of the standard of care, nor does it comprise all proper treatments or methods of care. It is not a substitute for a treating clinician’s independent professional judgment. Read ACOG’s complete disclaimer.
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