According to WebMD, women stop menstruating at different times, but most women stop in their 50s. When women stop menstruating for at least one year, they are said to be in menopause, which marks the end of their childbearing years.
WebMD states that the process leading up to menopause is called perimenopause. These changes in the body sometimes start as soon as the late 30s. Typically, perimenopause lasts for two to eight years. During this time, women are likely to experience irregular periods due to a fluctuation in hormone levels that is brought on by the body ovulating less frequently.
There are also some medical treatments and procedures that cause women to stop having periods before they reach menopause. WebMD lists these as removal of the ovaries, chemotherapy and radiation therapy.