No periods. Ovulation is the necessary step to have a spontaneous menstrual period. Following normal ovulation the hormone Progesterone rises significantly for roughly 2 weeks; if no pregnancy occurs, Progesterone falls and a period begins. In anovulation menstruation cannot occur, so periods are irregular or absent altogether. The only reliable symptom suggestive of anovulation is missed periods.
Irregular cycles. When ovulation is not taking place appropriately, the menstrual cycle will reflect that. In women who are anovulatory, their cycles will be irregular and unpredictable. Some women may even stop having periods altogether. Irregular cycles should be evaluated by your doctor to assess for the underlying cause.