During the years leading up to menopause, it is natural for periods to become more irregular and, therefore, less predictable. Whereas in years past your period may have come like clockwork, you may find yourself much more uncertain about when your period will arrive – and where you will be when protection is needed.
Perimenopause extends from age 45 years to age 55 years, although the timing varies among women. During this time, the ovaries produce less estrogen. Estrogen is the female hormone that controls how your body matures, your monthly periods, and body changes during pregnancy and breast-feeding.
Menopause, sometimes called "the change of life," marks the end of menstrual periods and of your childbearing years. On average, the age at which American women have their last menstrual period is 51 years. When a woman has gone one full year without a period, menopause is considered complete. At this point, any bleeding should be considered abnormal and should be called to a physician’s attention.3
3. Midlife Transitions: A guide to approaching menopause. October 2003. The American College of Obstetricians and Gynecologists.