The most common causes of late periods include pregnancy, excessive stress, thyroid and hormonal imbalances and the use of birth control, notes Women's Health magazine. Older women experiencing late periods may be entering the first stages of menopause.
Women who engage in extreme dieting and exercise habits run the risk of decreasing their overall body fat to such an extreme low, the body is no longer able to regulate its menstrual cycle. This is very common in females who suffer with anorexia and bulimia and is extremely unhealthy. It is the body's natural reaction to stressful conditions that causes it to prohibit ovulation to ensure a pregnancy cannot occur in a harsh environment.
Women diagnosed with polycystic ovarian syndrome suffer from imbalances in their estrogen, testosterone and progesterone levels. As a result, the body's normal systems are out of sync, and this makes it difficult to experience a consistent menstrual cycle. Chronic diseases that tax the body's resources are also likely to create a stressful environment that may impact the regularity of a woman's periods.
According to WebMD, some women simply never experience a steady menstrual cycle and may commonly see their periods start on random dates. It is important to visit with a doctor to analyze accompanying symptoms and perform any necessary tests to rule out serious underlying health concerns.