Usually, but not always, there is a growth spurt, growth and darkening of hair under the arms and of pubic hair and breast development preceding menstruation. Menstruation is also referred to as having your period. After your first period, the female body prepares for pregnancy each month. This process is controlled by various hormones that interact with each other. The body usually begins to produce these hormones between the ages of 10 to 13 years in females and this marks the beginning of puberty.
Menstruation is the discharge of blood and sometimes tissue through the vagina.
It comes from the uterus when the female is not pregnant and is caused by normal changes in hormone levels. When your period begins you will notice blood on your underwear. This is often frightening the first time it happens - don't worry, though, it is part of normal female development. Other things you may experience are bloating, swelling, moodiness or depression, headaches or backaches, changes in appetite, nausea, cramps, diarrhea, constipation, weight gain, skin blemishes, nervousness or fatigue. The menstrual cycle is the time between the first day of your period and the last day before your period begins.