It usually begins at about ages 12-13 and continues until a woman is about 50 years old. Menstruation, or the menstrual period, is the monthly bleeding that occurs as a part of a woman's reproductive cycle. Most women have mild cramps as the menstrual period begins-having such cramps for a day or two each month is usually normal.
Some women have severe pain.
Painful menstruation is called dysmenorrhoea. The causes of painful periods can be various. Dysmenorrhea is usually divided into two types- primary and secondary. The more common type, primary dysmenorrhoea, is due to the normal production of prostaglandins by the inner lining of the uterus. These prostaglandins make the uterus contract during the periods.