Perimenopause is the time during which your body makes the natural transition to menopause, marking the end of the reproductive years. It is also called the menopausal transition and begins several years before menopause. Women start perimenopause at different ages, but it usually starts in your mid-40s. However, it can start earlier, even in your mid-30s. Perimenopause lasts up until menopause, which is reached when a woman hasn’t had a period for one year. The average length of perimenopause is 4 years, but for some women, this stage may last only a few months or continue for 10 years.