While menopause used to invoke feelings of trepidation and confusion in many women, ideas about it have changed considerably. People now recognize that menopause is a natural biological process and not a medical illness. Yet, many women still deal with very real symptoms, such as hot flashes, mood swings, and decreased levels of energy. Fortunately, an understanding of the body's changes during this phase of life can help ease the transition and better prepare women to take charge of their health throughout the coming years. Here, a look at menopause by the numbers:

  • 12: Number of months of missed periods that must occur before a woman is considered to have reached menopause.

  • 51: Average age of the onset of menopause in the United States, according to the Hormone Foundation.

  • 1: Percentage of women who reach menopause before age 40.

  • 1 to 10: Number of years the entire menopausal transition may take, according to the Hormone Foundation.

  • 98: Percentage of women who experience four to eight years of menstrual cycle changes before they fully reach menopause, according to the North American Menopause Society.

  • 75: Percentage of women who experience hot flashes during menopause, according to the North American Menopause Society.

  • 3: Average length, in inches, of a woman's uterus.

  • 2: Number of hormones made in the ovaries that help to regulate a woman's monthly period.

  • 300: Approximate number of eggs in a woman's ovaries as she nears menopause, compared to the 1 to 2 million eggs she was born with.