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Why do periods become irregular during perimenopause?
Irregular periods during perimenopause are mainly caused by changes in hormone levels.
As the ovaries begin to slow down, the normal pattern of hormone release becomes less consistent, which affects the menstrual cycle.
How hormone fluctuations cause irregular periods
Oestrogen levels rise and fall unevenly during perimenopause. Instead of following a smooth monthly cycle, hormone levels can change unpredictably, which disrupts the timing of periods.
How irregular ovulation affects periods in perimenopause
In a typical cycle, ovulation happens once each month. During perimenopause, ovulation may not occur every cycle. When ovulation is irregular, periods often become irregular too.
How disrupted hormone signals affect the menstrual cycle
The menstrual cycle relies on a balance of hormones sending clear signals to the body. During perimenopause, these signals can become inconsistent, leading to cycles that are shorter, longer or missed.
Irregular periods and the transition to menopause
As the ovaries gradually produce fewer hormones, the menstrual cycle becomes more irregular over time. This continues until periods stop completely and, after a further 12 months of no periods, the menopause milestone is reached.
When to see a doctor
Irregular periods are common, but arranging a perimenopause consultation can provide clarity if you notice:
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bleeding between periods
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irregular bleeding that feels unusual for you
Key points
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Irregular periods are caused by changing hormone levels.
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Oestrogen fluctuations disrupt the normal cycle.
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Ovulation may not happen every month.
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Hormone signals become less consistent over time.
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Changes are part of the natural transition to menopause.
Medically reviewed by Dr Susana Rodriguez, menopause clinician at ClaraSana Women’s Health, Perth.
Our content is based on up-to-date Australian guidelines & may differ from information on other sites.