According to Reed and Carr a woman has a menstrual cycle that is approximately 36 days long would be described to have a oligomenorrheic cycle. Patients who experience menstrual cycles that occur at intervals less than 21 days are termed polymenorrheic, while patients who experience prolonged menstrual cycles greater than 35 days, are termed oligomenorrheic.The median duration of a menstrual cycle is 28 days.