Perimenopause Body Changes
To understand perimenopause, it helps to understand what your ovaries do throughout your reproductive years.
Your reproductive years
Your reproductive years are the time in a woman’s life when you can become pregnant and have children.
Your ovaries contain a limited pool of follicles – which are tiny fluid-filled sacs, each containing an egg.
Every month, several follicles compete to produce a dominant one that releases an egg during ovulation (which is the phase in the menstrual cycle when an egg is released).
The follicles also produce oestrogen and progesterone, which are key female hormones.
So, during your reproductive years, women’s bodies are used to certain levels of oestrogen and progesterone. For most women, their levels of oestrogen and progesterone are stable – which means the levels of oestrogen and progesterone we produce do not change much from month to month.
As you get older, the number and quality of these follicles decreases (drops) naturally – a process called ‘diminishing ovarian reserve’.
Then during perimenopause
In perimenopause, women begin to have more menstrual cycles when they do not ovulate (that is, they do not produce an egg). Therefore, little progesterone is produced during those menstrual cycles. Click here for more on what happens during perimenopause.
Progesterone is only produced in significant amounts after ovulation. If there is no egg in a cycle, little progesterone is produced.
When this happens, oestrogen continues to cause the lining of your womb or uterus to thicken, and when it eventually sheds (as your period), the result can be a much heavier flow than usual. This is why many women talk about having much heavier bleeding during perimenopause.
There are also changes in oestrogen levels. Overall, as the number of follicles decrease, our oestrogen levels drop over time. However, our oestrogen levels do not drop in a straightforward, smooth and steady way.
During the early and late perimenopause phases – there are swings or fluctuations in oestrogen and progesterone levels in unpredictable or erratic ways. This is different to your reproductive phase.
In late perimenopause especially, there are increased changes in the length of menstrual cycle, extreme hormonal swings/fluctuations and an increase in cycles where you do not produce an egg (ovulate).
This is what makes perimenopause – this time of transition before your final menstrual period – so tricky and gives rise to symptoms that women struggle with, as more studies are increasingly confirming.
There are other key hormones – including follicle stimulating hormone (FSH), inhibin B, Anti-Mullerian hormone (AMH) – that are also important for women’s menstrual cycles. There are also significant changes in the levels of inhibin B, AMH, FSH during perimenopause and menopause. An overview of this can be provided. Our intention is not to ignore the role of these hormones, and the changes that happen. Rather we are trying to communicate the main hormonal changes that are happening during this time in a way that all South African women can understand.1
My Menopause SA
Evidence-based menopause information for South African women.
Page last reviewed: 1 March 2026
Next review due: 1 March 2027