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Puberty (girls)

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Puberty (girls)

Written by Maryam Sharmanesh, GP

The change from girl to woman starts with early puberty and culminates in the first period. With these changes, come questions. We look at common issues around:

puberty

the menstrual cycle and periods

pregnancy and contraception

breasts

vaginal discharge

sexually transmitted diseases.

Puberty

When should puberty start? Puberty in girls usually starts at any time between 8 and 13 years of age, periods usually start about two years after the start of puberty.

What happens during puberty?

A girl grows and changes in ways that prepare her to be able to have a baby. These changes occur in certain stages.

First, girls can expect to develop breasts. These start from a small and often painful lump or 'bud' underneath the nipple. Breasts can take five years to reach their final size and shape. So girls, don't worry if your breasts do not currently match your idol from Baywatch.

Hair starts to grow under the arm and in the pubic (genital) area.

The explosive growth spurt: this is greater than any other time except the first year of life.

The body shape becomes curvier. During this time it is normal to put on weight, especially at the hips and stomach (puppy fat as it's rather insultingly called!) so don't go on a starvation diet.

The body odour can change especially under the arms, and you notice increased perspiration.

Some people get acne on the face and back.

Vaginal discharge starts or changes.

Teenagers experience a change in their emotions and new sexual feelings.

Periods start.

Why do these changes occur?

Natural chemicals that circulate in the body, called sex hormones, cause these changes. At the start of puberty, the brain releases a hormone known as gonadotrophin-releasing hormone (GnRH). This causes the release of two more hormones called follicle stimulating hormone (FSH) and luteinising hormone (LH) into the bloodstream. LH and FSH in turn stimulate the ovaries, which contain your eggs, to release the hormone oestrogen that leads to the changes girls go through during puberty.

The menstrual cycle and periods

What is a period? A period is the vaginal bleeding that women usually experience at regular intervals of about a month from puberty to menopause (the end of periods that, on average, occurs in your early 50s). Periods are also called menstruation.

Why do women have periods?

Periods are a part of the menstrual cycle that happens roughly every month to prepare a woman's body to have a baby.

Every woman has thousands of eggs in her ovaries. Once a month or so, one of these eggs matures and travels into the Fallopian tubes. These tubes propel the egg along towards the uterus (the womb), in the hope of meeting a sperm and becoming fertilized to become an embryo. If fertilized, the egg then continues its way along the tube and becomes implanted (embedded) in the uterus where it develops into a foetus. In this way, the woman becomes pregnant.

While the egg is on its travels, the uterus is being prepared for the implantation of the embryo. Its lining builds up to become cushion-like and engorged with blood. If the egg is not fertilized, the womb sheds this blood-filled lining, and this bleeding is what we call a period.

The cycle then repeats every month or so unless the woman becomes pregnant.

What controls the menstrual cycle?

Again, hormones control the process. The menstrual cycle can be split into four stages.

Menstrual (bleeding) phase: all the hormones are at their lowest level and consequently the womb sheds its lining and the woman has her period.

Pre-ovulatory phase: the ovary starts to secrete oestrogen, which leads to a gradual build up of the uterus lining in preparation for ovulation.

Ovulation: at a critical point roughly 14 days after the start of bleeding, the level of oestrogen reaches such a height that it causes the brain to release a large amount of LH, which in turn stimulates release of an egg from the ovaries.

Post-ovulatory phase: after the release of the egg, the ovaries produce another hormone, progesterone, which maintains the lining of the womb so a fertilized egg can implant. If the egg is not fertilised, progesterone and oestrogen levels drop, the womb loses its lining, and, about 14 days after ovulation, the menstrual phase begins again.

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