During puberty a girl will begin to menstruate.
This is called ovulation.
It is during ovulation that a girl can get pregnant.
If a sperm does not penetrate or impregnate a girl's egg cell then her period will begin in about 14 days.
A girl's menstrual cycle begins on the day she starts her period.
When girls first begin to menstruate, it is common for their periods to be irregular.
Some but not all girls suffer from side effects before or during their period-this is often called premenstrual syndrome (PMS).
Headaches
Backaches
Cramps
Water retention
Bloating
Depression
Breast tenderness
Acne or pimples
After a girl begins menstruating, she can keep track of her period by using a calendar.
* This information will allow a girl to estimate when her period will begin again so she won't be caught without protection-a pad or tampon.