Mother's age at menopause may influence female fertility

A woman's fertility may be strongly linked
to the age her mother was at menopause, according to research. Scientists estimate
that women whose mothers went through the menopause earlier in life - before
age 45 - are likely to have fewer eggs in their ovaries compared to women of the same age whose
mothers had a late menopause.

Women are born with all the eggs they
will ever produce and it is impossible to count how many eggs a woman has left
in her ovaries, a measure known as 'ovarian reserve'. Instead, the researchers relied
on accepted methods used by doctors to predict a woman's future fertility.
These methods are sometimes referred to as the 'biological body clock test' and
look at levels of anti-Mullerian hormone (AMH) in the women's blood and their antral
follicle count (AFC).

In the study, published in the journal Human Reproduction, 527 women aged between
20 and 40, were divided into groups depending on whether their mothers had
early, normal, or late menopause. Average levels of AMH declined by 8.6 percent,
6.8 percent, and 4.2 percent a year, respectively. Similar results were obtained
using the groups' AFC readings.

'This is the first study to suggest
that the age-related decline of AMH and AFC may differ between those whose mothers
entered menopause before the age of 45 years and those whose mothers entered
menopause after the age of 55', said lead researcher Dr Janne Bentzen, from the
Copenhagen University Hospital in Denmark. 'Our findings support the idea that
the ovarian reserve is influenced by hereditary factors'.

Other studies suggest there is about
a 20 year gap between the time a woman's fertility starts to decline and the
onset of menopause. This means women who enter menopause at 45 may have begun
their decline in fertility from as early as 25 years old.

'In line with the suggested 20 years
interval between the first decline in fertility and the menopause, we
hypothesised that maternal factors may also have an impact on a woman's
fertility potential', added Dr Bentzen.

However, other scientists have urged
caution when interpreting the findings of the present study, as the ovarian
reserve of individual women is subject to a large degree of variation. As a
result, many women will have fewer eggs and yet still may not encounter problems
becoming pregnant.

Dr Valentine Akande, consultant
gynaecologist and spokesman for the British Fertility Society told the BBC: 'Whilst
it is assumed that lower egg number is associated with more challenges at
getting pregnant, this study did not look at that'.

The
team behind the research
is now planning a five-year follow-up study to better gauge an individual
women's reproductive lifespan.