Menstrual cycle is counted from the first day of period to the first day of the next period. For most women the menstrual cycle is between 21 to 35 days.
On an average a period lasts between 3 to 5 days. It is normal for a girl to have irregular periods in the beginning. During this time, the duration of her periods may vary from as short as 2 days to as long as 7 days. It can take up to a year for periods to become regular.
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