Perimenopause
Perimenopause is the stage leading up to menopause, when the ovaries gradually begin to run out of eggs and hormone production starts to shift. It marks the transition toward the end of the reproductive years, although pregnancy is still possible during this time.
In Australia, the average age of menopause is around 51–52 years. Perimenopause often begins in a woman’s 40s and typically lasts four to six years, although for some women it can continue for up to ten years.
What happens during perimenopause?
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As the number of eggs in the ovaries declines, hormone levels - particularly oestrogen - begin to fluctuate. Rather than steadily declining, hormones can rise and fall unpredictably during this stage.
These hormonal fluctuations don’t just affect the ovaries - they also affect the brain, which is highly sensitive to changes in oestrogen. The brain prefers stability and does not respond well to hormonal chaos. As oestrogen rises and falls, it can disrupt brain signalling pathways that influence mood, sleep, memory and emotional regulation. Perimenopause often starts in the brain before it shows up in the menstrual cycle.
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Many women first notice changes such as brain fog, new anxiety, sleep disruption or mood changes, often before their menstrual cycles become irregular. Changes to the cycle typically appear later in the perimenopause transition.
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As hormonal fluctuations continue, menstrual cycles may begin to change. Periods can become irregular, heavier or lighter, shorter or longer and some cycles may be missed altogether. Ovulation may not occur every month and occasionally more than one ovulation can occur within a cycle.
You could think of it a bit like a farm season that becomes less predictable - some months everything runs smoothly and other months the weather changes overnight.