The best way to explain why a period happens is to explain the monthly cycle:
- Each month, hormones cause an egg (ova) in the ovaries to start maturing and be released from the ovary. This process is called ovulation.
- The egg moves along the fallopian tube towards the uterus. At the same time, the lining of the uterus becomes thick and soft with blood and tissue. This happens in anticipation of the egg being fertilised. If the egg is fertilised — the egg joins with a sperm — it will normally implant itself into the lining of the uterus and grow.
- When the egg is not fertilised, the lining of the uterus is not needed — so it sheds and comes out of the vagina. This is what people call a period.
Blood, cells from the lining of the uterus, cervical mucus, and vaginal discharge will all come out of the vagina during a period.
Most people lose between 4 and 12 teaspoons of blood each period.
The colour of the blood might change from red, to brown or black, towards the end of your period. This colour change is normal. The darker colour is a sign that the blood is slightly older — because it’s not leaving your body as quickly.
There might also be clots in your blood. Usually, your body tries to stop period blood from clotting — but if you have a heavy period, clots can form. If they are large (about the size of a $2 coin or larger), it’s a good idea to talk to one of our nurses or doctors.