Period

A period is the part of the menstrual cycle when a woman bleeds from her vagina for a few days.

The length of the menstrual cycle varies from woman to woman, but the average is to have periods every 28 days. Regular cycles that are longer or shorter than this, from 23 to 35 days, are normal.

The menstrual cycle is the time from the first day of a woman's period to the day before her next period.

Girls can start their periods anywhere from age 8 upwards, but the average is around 12 years. The average age for the menopause (when periods stop) in this country is 51.

Between the ages of 12 and 52, a woman will have around 480 periods, or fewer if she has any pregnancies.

To understand the menstrual cycle, it helps to know about the reproductive organs inside a woman's body. These are:

2 ovaries Ð where eggs are stored, developed and released
the womb (uterus) Ð where a fertilised egg implants and a baby develops
the fallopian tubes Ð two thin tubes that connect the ovaries to the womb
the cervix Ð the entrance to the womb from the vagina
the vagina

The menstrual cycle is controlled by hormones. In each cycle, rising levels of the hormone oestrogen cause the ovary to develop and release an egg (ovulation). The womb lining also starts to thicken.

In the second half of the cycle, the hormone progesterone helps the womb to prepare for implantation of a developing embryo.

The egg travels down the fallopian tubes. If pregnancy doesn't occur, the egg is reabsorbed into the body. Levels of oestrogen and progesterone fall, and the womb lining comes away and leaves the body as a period (the menstrual flow).

Ovulation is the release of an egg from the ovaries. A woman is born with all her eggs.

Once she starts her periods, 1 egg develops and is released during each menstrual cycle.

Pregnancy happens if a man's sperm meet and fertilise the egg. Sperm can survive in the fallopian tubes for up to 7 days after sex.

Occasionally, more than 1 egg is released during ovulation. If more than 1 egg is fertilised it can lead to a multiple pregnancy, such as twins.

Puberty

Puberty is when a child's body begins to develop and change as they become an adult.

Signs of puberty include girls developing breasts and starting periods, and boys developing a larger penis and testicles, a deeper voice and a more muscular appearance.

The average age for girls to start puberty is 11, while for boys the average age is 12.

But it's perfectly normal for puberty to begin at any point between the ages of 8 and 13 in girls and 9 and 14 in boys.

There's not usually any need to worry if puberty does not start around the average age, but it's a good idea to speak to your GP for advice if it starts before 8 or has not started by around 14.

In some cases, early puberty or delayed puberty could be a sign of an underlying condition that may need to be treated.

Early puberty, also called precocious puberty, is when:

girls have signs of puberty before 8 years of age
boys have signs of puberty before 9 years of age
Some girls and boys may develop certain signs of puberty at a young age, but not others.

For example, girls may start periods before the age of 8 but have no breast development.

See your GP if this happens to your child.

Talking about periods 

Try to talk about periods as an ongoing process rather than a formal sit-down talk.

You can use TV ads for tampons, or buying sanitary towels at the supermarket, for example, to start the conversation about periods. Or simply ask your daughter what she already knows and go from there.

Use clear language, like "vagina". Emphasise that periods are completely normal and natural Ð they're part of growing up.

Boys also need to learn about periods. Talk to them in the same way as girls about the practicalities, mood changes that can come with periods, and the biological reason behind periods. It will keep them informed, as well as help them to understand about periods.

When a girl starts her periods it's a sign that her body is now able to have a baby. It's important that she also knows about getting pregnant and contraception.