Just as our bodies changed during puberty and we began to menstruate, so again—usually at midlife—we transition from our reproductive years to the natural end of monthly menstrual cycles. The transition usually begins in our forties and ends by the early fifties, although any age from the late thirties to sixty can be normal.

Perimenopause is the one-to-ten-year stretch during which the ovaries function erratically and hormonal fluctuations may bring a range of changes, such as hot flashes, night sweats, sleep disturbances, and heavy menstrual bleeding. Perimenopause is a natural transition that affects each woman differently; for about 20 percent of us, the discomforts are so disruptive that we need major support and/or medical interventions.

Menopause is marked by the final menstrual period, known to be final after twelve months with no periods. After no flow for one year, the ovaries settle down and the reproductive hormones— estrogen and progesterone, which the body no longer needs for possible reproduction—have declined to low, steady levels. Most of us will live a third of our lives in what many call postmenopause.

Some of us reach the end of menstrual periods early owing to chemotherapy or radiation therapy, surgical removal of the ovaries, or special health conditions.