When girls cross puberty and enter sexual maturity, their reproductive cycle begins, in which a matured egg is released from the ovary every month. If the egg is not fertilized, it is released along with the inner lining of the uterus which causes the bleeding, known as menstrual period. During this period women bleed from their uterus or womb, via the vagina. Women start having their menstrual period between the age of 10 or 14 years and continue till they reach menopause around the age of 40 to 55 years. The ovulation cycle may vary from 21 to 35 days depending on the woman and other factors such as her weight, illness, medications and psychological factors as well.
Normally a menstrual period lasts between three and seven days and each menstrual period starts, after approximately 28 days unless the woman becomes pregnant during a particular cycle. The duration and flow of the menstrual period sometimes changes as the girl grows older and stabilize as she enters her twenties becoming more regular. Sometimes the periods may be late or the woman might even skip her period due to various reasons such as illness or medication. If the flow is extremely heavy, or the bleeding causes intense pain and cramp or goes on for more than a week, it is recommended to consult a doctor.
answered by M W