In most cases, when a period comes early it is nothing to worry about. However, according to Med Guidance, an early period may be a sign of the onset of menopause. Spotting and cramps that are easy to mistake for a period may also be early signs of pregnancy.
As explained by WebMD, stress, illness and even a sudden increase in altitude such as when a woman travels by plane can trigger an early period. Unless irregularity persists for several menstrual cycles in a row, an early period is generally not a sign of an underlying medical condition. A woman who is concerned about irregular periods or suspects she may be pregnant should talk to her physician.