Menses happens in the first days of the menstrual cycle. This is the changes that happen in a woman's body every month. These changes are started by changes in hormone levels in the blood. These changes also cause a person to ovulate and make an ovum (also called "egg"). Menstruation usually starts around the age of 11, even as early as 9 years old, and ends when the menstruator is too old to have children. However, some females can still have children from the age of 50-70.