Many women will experience menstrual irregularity throughout their childbearing years. According to the American Pregnancy Association, every woman's cycle is different, and therefore women should not compare their menstrual cycle to those of a sibling or friend. The average menstrual cycle ranges from 28 to 32 days. There may be a medical reason for menstrual irregularity. There are several reasons that a woman's period may be late if she is not pregnant.
Adolescence
Many adolescent girls experience irregular menstrual cycles for the first few years that they have their periods. This is considered a normal finding in young girls and should not cause immediate concern. However, if menstruation is accompanied by severe cramping, heavy bleeding, irritability, and mood swings, adolescents should consult a physician. Young girls should keep a calendar of their periods, including the first and last day and noting whether the bleeding was particularly light or heavy. In the event of a problem, having a written record will be beneficial to the physician providing treatment.
Medications
Certain medications may cause a period to be late and irregular. These medications include hormonal birth control methods such as the pill, ring, patch, shot, and intrauterine device. According to Medline, the use of certain drugs such as steroids or blood thinners may cause menstrual irregularity. Women who are on these medications and then stop taking them may experience menstrual irregularity until the medication is out of their system. In some cases, it may take several weeks or months for the body's regular menstrual cycle to return.
Stress and Changes in Weight
Women who are under a great deal of emotional and physical stress may experience late menstrual periods. Stress causes a fluctuation in the body's normal hormonal balance and can easily affect monthly menstruation. Mild exercise, yoga, meditation, and massage can help to relieve stress naturally. A significant weight gain or loss may also alter a woman's menstrual cycle. Women who take up a new exercise regimen can experience irregular menstruation until their body adjusts to their new routine.
