Perimenopause, or menopausal transition, is the beginning of a woman's transition into menopause. It begins a few years before menopause when the ovaries start to decrease in their estrogen production. This means that a woman will begin to experience irregular menstrual cycles in addition to other menopausal symptoms which include: hot flashes, breast tenderness, lowered libido, fatigue, vaginal dryness, mood swings, and urinary leakage.
The age at which perimenopause occurs differs greatly from woman to woman. It usually starts in a woman's 40s, but it can occur even earlier, in her 30s. The average perimenopause phase lasts four years, but it can last up to 10 years.
Perimenopause ends when a woman has stopped ovulating completely and has not gotten a period for 12 months. She then enters the phase known as menopause.