Menopause happens gradually. The menopausal transition phase is called perimenopause (literally meaning “around menopause”). Perimenopause is defined as the period of your life shortly before menopause, when your body gradually begins to produce less estrogen, and your body begins to show the physical symptoms of menopause. Perimenopause begins many years before the last year of your menstrual period. Perimenopause can last six years or more, and ends one year after the final menstrual period.