For young adults

Why do we have periods?

As we grow, our bodies change so that we can have children - if the time is right, and if we want to.

Although we can’t see it, changes happen inside us. Our ovaries start to release eggs into the womb, or uterus.

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.

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

We can have periods from puberty until the menopause. All of our bodies are different, so some of us become fertile, or able to have children, earlier than others. It doesn’t mean that we should start to have children - just that our bodies are prepared for it.

We enter the menopause at different times, too - the stage in our older lives when we 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...

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