According to HealthCentral, experiencing more stress than usual is a common reason for woman to have a late or missed menstrual period. High stress levels can cause ovulation to not occur or to be delayed, and not ovulating can result in a missed period.
According to the Palo Alto Medical Foundation, there are many reasons other than pregnancy that cause a woman to have a late or missed period. Excessive exercise, weight changes and going on or off of hormonal birth control can cause irregular periods. If a woman does not have a period for more than six months, she is considered to have amenorrhea, which can be caused by various hormonal imbalances.