Perimenopause is the transition leading up to menopause. It often begins during a woman’s 40s, although it can begin earlier or later. During this transition, the ovaries change how they produce estrogen and progesterone. Hormone levels may rise and fall unpredictably rather than declining in a smooth, steady pattern. A woman has reached menopause after going 12 consecutive months without a menstrual period. Before that point, perimenopause can continue for several years.
