Perimenopause is the period leading up to menopause when a woman's hormone levels begin to fluctuate and when her menstrual cycle may become irregular. It can last anywhere from a few months to several years.
As women age, and reach perimenopause, their fertility declines, and the chances of getting pregnant gradually decrease. A woman is born with about 400000 ovarian follicles and these follicles are exhausted by the time she reaches perimenopause.
You may still ovulate and release eggs erratically making it less frequent and unpredictable. The quality of eggs may also decline, which can make it more difficult to conceive.
So while it is difficult for women to conceive, an unwanted pregnancy due to an erratic ovulation is not too uncommon. Therefore, it is important for women in perimenopause who do not wish to become pregnant to continue using contraception till they have gone through menopause and until a year after they have not had a period for 12 consecutive months.