For parents

Why women have periods

As they grow into adults, girls’ bodies change so that they can have children - when the time is right, and if they want to.

Although we can’t see it, changes happen inside. Their ovaries start to release eggs into the womb, or uterus. For most, this begins to happen between the ages of 11 to 14, although everyone’s a little different. When your daughter is young, eggs can be released at irregular times. By their late teens, most young adults find that an egg is released every 28 days.

Every month, before an egg is released, the womb - or uterus - begins to prepare for it. It builds up a thicker lining around its walls, a little like a cushion. If your daughter feels twinges or pains in the days before her bleeding starts, she may be feeling this lining build up.

When the egg is finally released, it sticks to this new lining. If a woman is old enough to have sex, the egg may be fertilised, and begin to develop into a foetus - the earliest stage of pregnancy. Most eggs aren’t fertilised. When the egg is unfertilised, the uterus begins to lose its lining after a few days. Young adults and women experience this as the blood flow that comes once a month.

Women can have periods from puberty until the menopause. All bodies are different, so some young adults become fertile, or able to have children, earlier than others.

Women enter the menopause at different times, too - the stage in their older lives when they lose the ability to become pregnant. For most women, the menopause happens in the late 40s to early 50s, but there can be a lot of variation.

If you’d like to learn more, take a look at our animation, Your Menstrual Cycle .

What causes period pain?

What causes period pain?

When an egg is unfertilised, the womb’s lining isn’t needed any more. So, the body releases hormones called prostaglandins.
They signal the muscles in the womb to contract...

Read more