A woman's menstrual cycle is as unique to her as her fingerprint. Ovulation and menstruation usually begin between the ages of 10-16 for most girls. The beginning of a woman's menstrual cycle, called menarche, is one of the most common causes of irregular menstruation because it may take up to two years for menstruation to become regular and a missed period here and there is a common occurrence. As a woman matures and ages, she eventually enters perimenopause, the beginning of menopause or the end of menstruation.

Perimenopause is another of the most common causes of irregular menstruation. During the years between the beginning of menstruation and menopause, many women experience an occasional missed period, but chronic irregular menstruation or heavy painful periods comprise a disruption of the hormonal signals that regulate a woman's menstrual cycle.