Understanding the Normal Menstrual Cycle

Having a period (menstruation) is a normal, healthy part of being a woman. It's also part of the menstrual cycle, a process that makes it possible for women to become pregnant.

An Egg Is Released

Eggs are female reproductive cells stored in the ovaries. During each cycle, one egg matures and is released from an ovary. This is called ovulation. The egg then travels from the ovary to a fallopian tube.

The Egg Travels Through a Tube

The egg moves through the fallopian tube toward the uterus. If sperm are present in the tube, the egg may be fertilized, resulting in pregnancy.

The Uterine Lining Grows Thicker

The lining of the uterus is made up of blood, tissue, and fluid. During each cycle, the lining thickens. This helps prepare the uterus to receive and nourish a fertilized egg. 

The Egg and Lining Are Shed

If pregnancy doesn't occur, the egg and thickened lining of the uterus are no longer needed. They are then shed through the vagina. This is called a period.

How Long Is Each Cycle?

It is normal for a cycle to take 20 to 36 days. For teenagers, the time between periods might be more or less. For adults, it will be around a month from the first day of one period to the first day of the next. That's why you may hear women talk about a "monthly cycle."

How Long Does a Period Last?

It's normal for a period to last 2 to 8 days. Talk to your doctor if your period lasts longer than 8 days for 2 cycles in a row.