What is Perimenopause

https://www.nivabupa.com/disease-articles/what-is-perimenopause-symptoms-causes-and-treatment.html

Perimenopause is the transitional phase before menopause when a woman's body begins to make less estrogen. It usually occurs in the 40s but can start earlier. During this time, periods become irregular, and symptoms like hot flashes, mood swings, and sleep disturbances may occur, what is perimenopause? It's the body's natural progression toward the end of reproductive years.